dotemacs

dash.info (193918B)

---

 This is dash.info, produced by makeinfo version 6.5 from dash.texi.
 
 This manual is for Dash version 2.19.1.
 
    Copyright © 2012–2021 Free Software Foundation, Inc.
 
      Permission is granted to copy, distribute and/or modify this
      document under the terms of the GNU Free Documentation License,
      Version 1.3 or any later version published by the Free Software
      Foundation; with the Invariant Sections being “GNU General Public
      License,” and no Front-Cover Texts or Back-Cover Texts.  A copy of
      the license is included in the section entitled “GNU Free
      Documentation License”.
 INFO-DIR-SECTION Emacs
 START-INFO-DIR-ENTRY
 * Dash: (dash.info).    A modern list library for GNU Emacs.
 END-INFO-DIR-ENTRY
 
 
 File: dash.info,  Node: Top,  Next: Installation,  Up: (dir)
 
 Dash
 ****
 
 This manual is for Dash version 2.19.1.
 
    Copyright © 2012–2021 Free Software Foundation, Inc.
 
      Permission is granted to copy, distribute and/or modify this
      document under the terms of the GNU Free Documentation License,
      Version 1.3 or any later version published by the Free Software
      Foundation; with the Invariant Sections being “GNU General Public
      License,” and no Front-Cover Texts or Back-Cover Texts.  A copy of
      the license is included in the section entitled “GNU Free
      Documentation License”.
 
 * Menu:
 
 * Installation::        Installing and configuring Dash.
 * Functions::           Dash API reference.
 * Development::         Contributing to Dash development.
 
 Appendices
 
 * FDL::                 The license for this documentation.
 * GPL::                 Conditions for copying and changing Dash.
 * Index::               Index including functions and macros.
 
  — The Detailed Node Listing —
 
 Installation
 
 * Using in a package::  Listing Dash as a package dependency.
 * Fontification of special variables::  Font Lock of anaphoric macro variables.
 * Info symbol lookup::  Looking up Dash symbols in this manual.
 
 Functions
 
 * Maps::
 * Sublist selection::
 * List to list::
 * Reductions::
 * Unfolding::
 * Predicates::
 * Partitioning::
 * Indexing::
 * Set operations::
 * Other list operations::
 * Tree operations::
 * Threading macros::
 * Binding::
 * Side effects::
 * Destructive operations::
 * Function combinators::
 
 Development
 
 * Contribute::          How to contribute.
 * Contributors::        List of contributors.
 
 
 File: dash.info,  Node: Installation,  Next: Functions,  Prev: Top,  Up: Top
 
 1 Installation
 **************
 
 Dash is available on GNU ELPA (https://elpa.gnu.org/), GNU-devel ELPA
 (https://elpa.gnu.org/devel/), and MELPA (https://melpa.org/), and can
 be installed with the standard command ‘package-install’ (*note
 (emacs)Package Installation::).
 
 ‘M-x package-install <RET> dash <RET>’
      Install the Dash library.
 
    Alternatively, you can just dump ‘dash.el’ in your ‘load-path’
 somewhere (*note (emacs)Lisp Libraries::).
 
 * Menu:
 
 * Using in a package::  Listing Dash as a package dependency.
 * Fontification of special variables::  Font Lock of anaphoric macro variables.
 * Info symbol lookup::  Looking up Dash symbols in this manual.
 
 
 File: dash.info,  Node: Using in a package,  Next: Fontification of special variables,  Up: Installation
 
 1.1 Using in a package
 ======================
 
 If you use Dash in your own package, be sure to list it as a dependency
 in the library’s headers as follows (*note (elisp)Library Headers::).
 
      ;; Package-Requires: ((dash "2.19.1"))
 
 
 File: dash.info,  Node: Fontification of special variables,  Next: Info symbol lookup,  Prev: Using in a package,  Up: Installation
 
 1.2 Fontification of special variables
 ======================================
 
 The autoloaded minor mode ‘dash-fontify-mode’ is provided for optional
 fontification of anaphoric Dash variables (‘it’, ‘acc’, etc.) in Emacs
 Lisp buffers using search-based Font Lock (*note (emacs)Font Lock::).
 In older Emacs versions which do not dynamically detect macros, the
 minor mode also fontifies calls to Dash macros.
 
    To automatically enable the minor mode in all Emacs Lisp buffers,
 just call its autoloaded global counterpart ‘global-dash-fontify-mode’,
 either interactively or from your ‘user-init-file’:
 
      (global-dash-fontify-mode)
 
 
 File: dash.info,  Node: Info symbol lookup,  Prev: Fontification of special variables,  Up: Installation
 
 1.3 Info symbol lookup
 ======================
 
 While editing Elisp files, you can use ‘C-h S’ (‘info-lookup-symbol’) to
 look up Elisp symbols in the relevant Info manuals (*note (emacs)Info
 Lookup::).  To enable the same for Dash symbols, use the command
 ‘dash-register-info-lookup’.  It can be called directly when needed, or
 automatically from your ‘user-init-file’.  For example:
 
      (with-eval-after-load 'info-look
        (dash-register-info-lookup))
 
 
 File: dash.info,  Node: Functions,  Next: Development,  Prev: Installation,  Up: Top
 
 2 Functions
 ***********
 
 This chapter contains reference documentation for the Dash API
 (Application Programming Interface).  The names of all public functions
 defined in the library are prefixed with a dash character (‘-’).
 
    The library also provides anaphoric macro versions of functions where
 that makes sense.  The names of these macros are prefixed with two
 dashes (‘--’) instead of one.
 
    For instance, while the function ‘-map’ applies a function to each
 element of a list, its anaphoric counterpart ‘--map’ evaluates a form
 with the local variable ‘it’ temporarily bound to the current list
 element instead.
 
      ;; Normal version.
      (-map (lambda (n) (* n n)) '(1 2 3 4))
          ⇒ (1 4 9 16)
 
      ;; Anaphoric version.
      (--map (* it it) '(1 2 3 4))
          ⇒ (1 4 9 16)
 
    The normal version can, of course, also be written as in the
 following example, which demonstrates the utility of both versions.
 
      (defun my-square (n)
        "Return N multiplied by itself."
        (* n n))
 
      (-map #'my-square '(1 2 3 4))
          ⇒ (1 4 9 16)
 
 * Menu:
 
 * Maps::
 * Sublist selection::
 * List to list::
 * Reductions::
 * Unfolding::
 * Predicates::
 * Partitioning::
 * Indexing::
 * Set operations::
 * Other list operations::
 * Tree operations::
 * Threading macros::
 * Binding::
 * Side effects::
 * Destructive operations::
 * Function combinators::
 
 
 File: dash.info,  Node: Maps,  Next: Sublist selection,  Up: Functions
 
 2.1 Maps
 ========
 
 Functions in this category take a transforming function, which is then
 applied sequentially to each or selected elements of the input list.
 The results are collected in order and returned as a new list.
 
  -- Function: -map (fn list)
      Apply FN to each item in LIST and return the list of results.
 
      This function’s anaphoric counterpart is ‘--map’.
 
           (-map (lambda (num) (* num num)) '(1 2 3 4))
               ⇒ (1 4 9 16)
           (-map #'1+ '(1 2 3 4))
               ⇒ (2 3 4 5)
           (--map (* it it) '(1 2 3 4))
               ⇒ (1 4 9 16)
 
  -- Function: -map-when (pred rep list)
      Return a new list where the elements in LIST that do not match the
      PRED function are unchanged, and where the elements in LIST that do
      match the PRED function are mapped through the REP function.
 
      Alias: ‘-replace-where’
 
      See also: ‘-update-at’ (*note -update-at::)
 
           (-map-when 'even? 'square '(1 2 3 4))
               ⇒ (1 4 3 16)
           (--map-when (> it 2) (* it it) '(1 2 3 4))
               ⇒ (1 2 9 16)
           (--map-when (= it 2) 17 '(1 2 3 4))
               ⇒ (1 17 3 4)
 
  -- Function: -map-first (pred rep list)
      Replace first item in LIST satisfying PRED with result of REP
      called on this item.
 
      See also: ‘-map-when’ (*note -map-when::), ‘-replace-first’ (*note
      -replace-first::)
 
           (-map-first 'even? 'square '(1 2 3 4))
               ⇒ (1 4 3 4)
           (--map-first (> it 2) (* it it) '(1 2 3 4))
               ⇒ (1 2 9 4)
           (--map-first (= it 2) 17 '(1 2 3 2))
               ⇒ (1 17 3 2)
 
  -- Function: -map-last (pred rep list)
      Replace last item in LIST satisfying PRED with result of REP called
      on this item.
 
      See also: ‘-map-when’ (*note -map-when::), ‘-replace-last’ (*note
      -replace-last::)
 
           (-map-last 'even? 'square '(1 2 3 4))
               ⇒ (1 2 3 16)
           (--map-last (> it 2) (* it it) '(1 2 3 4))
               ⇒ (1 2 3 16)
           (--map-last (= it 2) 17 '(1 2 3 2))
               ⇒ (1 2 3 17)
 
  -- Function: -map-indexed (fn list)
      Apply FN to each index and item in LIST and return the list of
      results.  This is like ‘-map’ (*note -map::), but FN takes two
      arguments: the index of the current element within LIST, and the
      element itself.
 
      This function’s anaphoric counterpart is ‘--map-indexed’.
 
      For a side-effecting variant, see also ‘-each-indexed’ (*note
      -each-indexed::).
 
           (-map-indexed (lambda (index item) (- item index)) '(1 2 3 4))
               ⇒ (1 1 1 1)
           (--map-indexed (- it it-index) '(1 2 3 4))
               ⇒ (1 1 1 1)
           (-map-indexed #'* '(1 2 3 4))
               ⇒ (0 2 6 12)
 
  -- Function: -annotate (fn list)
      Return a list of cons cells where each cell is FN applied to each
      element of LIST paired with the unmodified element of LIST.
 
           (-annotate '1+ '(1 2 3))
               ⇒ ((2 . 1) (3 . 2) (4 . 3))
           (-annotate 'length '(("h" "e" "l" "l" "o") ("hello" "world")))
               ⇒ ((5 "h" "e" "l" "l" "o") (2 "hello" "world"))
           (--annotate (< 1 it) '(0 1 2 3))
               ⇒ ((nil . 0) (nil . 1) (t . 2) (t . 3))
 
  -- Function: -splice (pred fun list)
      Splice lists generated by FUN in place of elements matching PRED in
      LIST.
 
      FUN takes the element matching PRED as input.
 
      This function can be used as replacement for ‘,@’ in case you need
      to splice several lists at marked positions (for example with
      keywords).
 
      See also: ‘-splice-list’ (*note -splice-list::), ‘-insert-at’
      (*note -insert-at::)
 
           (-splice 'even? (lambda (x) (list x x)) '(1 2 3 4))
               ⇒ (1 2 2 3 4 4)
           (--splice 't (list it it) '(1 2 3 4))
               ⇒ (1 1 2 2 3 3 4 4)
           (--splice (equal it :magic) '((list of) (magical) (code)) '((foo) (bar) :magic (baz)))
               ⇒ ((foo) (bar) (list of) (magical) (code) (baz))
 
  -- Function: -splice-list (pred new-list list)
      Splice NEW-LIST in place of elements matching PRED in LIST.
 
      See also: ‘-splice’ (*note -splice::), ‘-insert-at’ (*note
      -insert-at::)
 
           (-splice-list 'keywordp '(a b c) '(1 :foo 2))
               ⇒ (1 a b c 2)
           (-splice-list 'keywordp nil '(1 :foo 2))
               ⇒ (1 2)
           (--splice-list (keywordp it) '(a b c) '(1 :foo 2))
               ⇒ (1 a b c 2)
 
  -- Function: -mapcat (fn list)
      Return the concatenation of the result of mapping FN over LIST.
      Thus function FN should return a list.
 
           (-mapcat 'list '(1 2 3))
               ⇒ (1 2 3)
           (-mapcat (lambda (item) (list 0 item)) '(1 2 3))
               ⇒ (0 1 0 2 0 3)
           (--mapcat (list 0 it) '(1 2 3))
               ⇒ (0 1 0 2 0 3)
 
  -- Function: -copy (list)
      Create a shallow copy of LIST.
 
           (-copy '(1 2 3))
               ⇒ (1 2 3)
           (let ((a '(1 2 3))) (eq a (-copy a)))
               ⇒ nil
 
 
 File: dash.info,  Node: Sublist selection,  Next: List to list,  Prev: Maps,  Up: Functions
 
 2.2 Sublist selection
 =====================
 
 Functions returning a sublist of the original list.
 
  -- Function: -filter (pred list)
      Return a new list of the items in LIST for which PRED returns
      non-nil.
 
      Alias: ‘-select’.
 
      This function’s anaphoric counterpart is ‘--filter’.
 
      For similar operations, see also ‘-keep’ (*note -keep::) and
      ‘-remove’ (*note -remove::).
 
           (-filter (lambda (num) (= 0 (% num 2))) '(1 2 3 4))
               ⇒ (2 4)
           (-filter #'natnump '(-2 -1 0 1 2))
               ⇒ (0 1 2)
           (--filter (= 0 (% it 2)) '(1 2 3 4))
               ⇒ (2 4)
 
  -- Function: -remove (pred list)
      Return a new list of the items in LIST for which PRED returns nil.
 
      Alias: ‘-reject’.
 
      This function’s anaphoric counterpart is ‘--remove’.
 
      For similar operations, see also ‘-keep’ (*note -keep::) and
      ‘-filter’ (*note -filter::).
 
           (-remove (lambda (num) (= 0 (% num 2))) '(1 2 3 4))
               ⇒ (1 3)
           (-remove #'natnump '(-2 -1 0 1 2))
               ⇒ (-2 -1)
           (--remove (= 0 (% it 2)) '(1 2 3 4))
               ⇒ (1 3)
 
  -- Function: -remove-first (pred list)
      Remove the first item from LIST for which PRED returns non-nil.
      This is a non-destructive operation, but only the front of LIST
      leading up to the removed item is a copy; the rest is LIST’s
      original tail.  If no item is removed, then the result is a
      complete copy.
 
      Alias: ‘-reject-first’.
 
      This function’s anaphoric counterpart is ‘--remove-first’.
 
      See also ‘-map-first’ (*note -map-first::), ‘-remove-item’ (*note
      -remove-item::), and ‘-remove-last’ (*note -remove-last::).
 
           (-remove-first #'natnump '(-2 -1 0 1 2))
               ⇒ (-2 -1 1 2)
           (-remove-first #'stringp '(1 2 "first" "second"))
               ⇒ (1 2 "second")
           (--remove-first (> it 3) '(1 2 3 4 5 6))
               ⇒ (1 2 3 5 6)
 
  -- Function: -remove-last (pred list)
      Remove the last item from LIST for which PRED returns non-nil.  The
      result is a copy of LIST regardless of whether an element is
      removed.
 
      Alias: ‘-reject-last’.
 
      This function’s anaphoric counterpart is ‘--remove-last’.
 
      See also ‘-map-last’ (*note -map-last::), ‘-remove-item’ (*note
      -remove-item::), and ‘-remove-first’ (*note -remove-first::).
 
           (-remove-last #'natnump '(1 3 5 4 7 8 10 -11))
               ⇒ (1 3 5 4 7 8 -11)
           (-remove-last #'stringp '(1 2 "last" "second"))
               ⇒ (1 2 "last")
           (--remove-last (> it 3) '(1 2 3 4 5 6 7 8 9 10))
               ⇒ (1 2 3 4 5 6 7 8 9)
 
  -- Function: -remove-item (item list)
      Return a copy of LIST with all occurrences of ITEM removed.  The
      comparison is done with ‘equal’.
 
           (-remove-item 3 '(1 2 3 2 3 4 5 3))
               ⇒ (1 2 2 4 5)
           (-remove-item 'foo '(foo bar baz foo))
               ⇒ (bar baz)
           (-remove-item "bob" '("alice" "bob" "eve" "bob"))
               ⇒ ("alice" "eve")
 
  -- Function: -non-nil (list)
      Return a copy of LIST with all nil items removed.
 
           (-non-nil '(nil 1 nil 2 nil nil 3 4 nil 5 nil))
               ⇒ (1 2 3 4 5)
           (-non-nil '((nil)))
               ⇒ ((nil))
           (-non-nil ())
               ⇒ ()
 
  -- Function: -slice (list from &optional to step)
      Return copy of LIST, starting from index FROM to index TO.
 
      FROM or TO may be negative.  These values are then interpreted
      modulo the length of the list.
 
      If STEP is a number, only each STEPth item in the resulting section
      is returned.  Defaults to 1.
 
           (-slice '(1 2 3 4 5) 1)
               ⇒ (2 3 4 5)
           (-slice '(1 2 3 4 5) 0 3)
               ⇒ (1 2 3)
           (-slice '(1 2 3 4 5 6 7 8 9) 1 -1 2)
               ⇒ (2 4 6 8)
 
  -- Function: -take (n list)
      Return a copy of the first N items in LIST.  Return a copy of LIST
      if it contains N items or fewer.  Return nil if N is zero or less.
 
      See also: ‘-take-last’ (*note -take-last::).
 
           (-take 3 '(1 2 3 4 5))
               ⇒ (1 2 3)
           (-take 17 '(1 2 3 4 5))
               ⇒ (1 2 3 4 5)
           (-take 0 '(1 2 3 4 5))
               ⇒ ()
 
  -- Function: -take-last (n list)
      Return a copy of the last N items of LIST in order.  Return a copy
      of LIST if it contains N items or fewer.  Return nil if N is zero
      or less.
 
      See also: ‘-take’ (*note -take::).
 
           (-take-last 3 '(1 2 3 4 5))
               ⇒ (3 4 5)
           (-take-last 17 '(1 2 3 4 5))
               ⇒ (1 2 3 4 5)
           (-take-last 1 '(1 2 3 4 5))
               ⇒ (5)
 
  -- Function: -drop (n list)
      Return the tail (not a copy) of LIST without the first N items.
      Return nil if LIST contains N items or fewer.  Return LIST if N is
      zero or less.
 
      For another variant, see also ‘-drop-last’ (*note -drop-last::).
 
           (-drop 3 '(1 2 3 4 5))
               ⇒ (4 5)
           (-drop 17 '(1 2 3 4 5))
               ⇒ ()
           (-drop 0 '(1 2 3 4 5))
               ⇒ (1 2 3 4 5)
 
  -- Function: -drop-last (n list)
      Return a copy of LIST without its last N items.  Return a copy of
      LIST if N is zero or less.  Return nil if LIST contains N items or
      fewer.
 
      See also: ‘-drop’ (*note -drop::).
 
           (-drop-last 3 '(1 2 3 4 5))
               ⇒ (1 2)
           (-drop-last 17 '(1 2 3 4 5))
               ⇒ ()
           (-drop-last 0 '(1 2 3 4 5))
               ⇒ (1 2 3 4 5)
 
  -- Function: -take-while (pred list)
      Take successive items from LIST for which PRED returns non-nil.
      PRED is a function of one argument.  Return a new list of the
      successive elements from the start of LIST for which PRED returns
      non-nil.
 
      This function’s anaphoric counterpart is ‘--take-while’.
 
      For another variant, see also ‘-drop-while’ (*note -drop-while::).
 
           (-take-while #'even? '(1 2 3 4))
               ⇒ ()
           (-take-while #'even? '(2 4 5 6))
               ⇒ (2 4)
           (--take-while (< it 4) '(1 2 3 4 3 2 1))
               ⇒ (1 2 3)
 
  -- Function: -drop-while (pred list)
      Drop successive items from LIST for which PRED returns non-nil.
      PRED is a function of one argument.  Return the tail (not a copy)
      of LIST starting from its first element for which PRED returns nil.
 
      This function’s anaphoric counterpart is ‘--drop-while’.
 
      For another variant, see also ‘-take-while’ (*note -take-while::).
 
           (-drop-while #'even? '(1 2 3 4))
               ⇒ (1 2 3 4)
           (-drop-while #'even? '(2 4 5 6))
               ⇒ (5 6)
           (--drop-while (< it 4) '(1 2 3 4 3 2 1))
               ⇒ (4 3 2 1)
 
  -- Function: -select-by-indices (indices list)
      Return a list whose elements are elements from LIST selected as
      ‘(nth i list)‘ for all i from INDICES.
 
           (-select-by-indices '(4 10 2 3 6) '("v" "e" "l" "o" "c" "i" "r" "a" "p" "t" "o" "r"))
               ⇒ ("c" "o" "l" "o" "r")
           (-select-by-indices '(2 1 0) '("a" "b" "c"))
               ⇒ ("c" "b" "a")
           (-select-by-indices '(0 1 2 0 1 3 3 1) '("f" "a" "r" "l"))
               ⇒ ("f" "a" "r" "f" "a" "l" "l" "a")
 
  -- Function: -select-columns (columns table)
      Select COLUMNS from TABLE.
 
      TABLE is a list of lists where each element represents one row.  It
      is assumed each row has the same length.
 
      Each row is transformed such that only the specified COLUMNS are
      selected.
 
      See also: ‘-select-column’ (*note -select-column::),
      ‘-select-by-indices’ (*note -select-by-indices::)
 
           (-select-columns '(0 2) '((1 2 3) (a b c) (:a :b :c)))
               ⇒ ((1 3) (a c) (:a :c))
           (-select-columns '(1) '((1 2 3) (a b c) (:a :b :c)))
               ⇒ ((2) (b) (:b))
           (-select-columns nil '((1 2 3) (a b c) (:a :b :c)))
               ⇒ (nil nil nil)
 
  -- Function: -select-column (column table)
      Select COLUMN from TABLE.
 
      TABLE is a list of lists where each element represents one row.  It
      is assumed each row has the same length.
 
      The single selected column is returned as a list.
 
      See also: ‘-select-columns’ (*note -select-columns::),
      ‘-select-by-indices’ (*note -select-by-indices::)
 
           (-select-column 1 '((1 2 3) (a b c) (:a :b :c)))
               ⇒ (2 b :b)
 
 
 File: dash.info,  Node: List to list,  Next: Reductions,  Prev: Sublist selection,  Up: Functions
 
 2.3 List to list
 ================
 
 Functions returning a modified copy of the input list.
 
  -- Function: -keep (fn list)
      Return a new list of the non-nil results of applying FN to each
      item in LIST.  Like ‘-filter’ (*note -filter::), but returns the
      non-nil results of FN instead of the corresponding elements of
      LIST.
 
      Its anaphoric counterpart is ‘--keep’.
 
           (-keep #'cdr '((1 2 3) (4 5) (6)))
               ⇒ ((2 3) (5))
           (-keep (lambda (n) (and (> n 3) (* 10 n))) '(1 2 3 4 5 6))
               ⇒ (40 50 60)
           (--keep (and (> it 3) (* 10 it)) '(1 2 3 4 5 6))
               ⇒ (40 50 60)
 
  -- Function: -concat (&rest lists)
      Return a new list with the concatenation of the elements in the
      supplied LISTS.
 
           (-concat '(1))
               ⇒ (1)
           (-concat '(1) '(2))
               ⇒ (1 2)
           (-concat '(1) '(2 3) '(4))
               ⇒ (1 2 3 4)
 
  -- Function: -flatten (l)
      Take a nested list L and return its contents as a single, flat
      list.
 
      Note that because ‘nil’ represents a list of zero elements (an
      empty list), any mention of nil in L will disappear after
      flattening.  If you need to preserve nils, consider ‘-flatten-n’
      (*note -flatten-n::) or map them to some unique symbol and then map
      them back.
 
      Conses of two atoms are considered "terminals", that is, they
      aren’t flattened further.
 
      See also: ‘-flatten-n’ (*note -flatten-n::)
 
           (-flatten '((1)))
               ⇒ (1)
           (-flatten '((1 (2 3) (((4 (5)))))))
               ⇒ (1 2 3 4 5)
           (-flatten '(1 2 (3 . 4)))
               ⇒ (1 2 (3 . 4))
 
  -- Function: -flatten-n (num list)
      Flatten NUM levels of a nested LIST.
 
      See also: ‘-flatten’ (*note -flatten::)
 
           (-flatten-n 1 '((1 2) ((3 4) ((5 6)))))
               ⇒ (1 2 (3 4) ((5 6)))
           (-flatten-n 2 '((1 2) ((3 4) ((5 6)))))
               ⇒ (1 2 3 4 (5 6))
           (-flatten-n 3 '((1 2) ((3 4) ((5 6)))))
               ⇒ (1 2 3 4 5 6)
 
  -- Function: -replace (old new list)
      Replace all OLD items in LIST with NEW.
 
      Elements are compared using ‘equal’.
 
      See also: ‘-replace-at’ (*note -replace-at::)
 
           (-replace 1 "1" '(1 2 3 4 3 2 1))
               ⇒ ("1" 2 3 4 3 2 "1")
           (-replace "foo" "bar" '("a" "nice" "foo" "sentence" "about" "foo"))
               ⇒ ("a" "nice" "bar" "sentence" "about" "bar")
           (-replace 1 2 nil)
               ⇒ nil
 
  -- Function: -replace-first (old new list)
      Replace the first occurrence of OLD with NEW in LIST.
 
      Elements are compared using ‘equal’.
 
      See also: ‘-map-first’ (*note -map-first::)
 
           (-replace-first 1 "1" '(1 2 3 4 3 2 1))
               ⇒ ("1" 2 3 4 3 2 1)
           (-replace-first "foo" "bar" '("a" "nice" "foo" "sentence" "about" "foo"))
               ⇒ ("a" "nice" "bar" "sentence" "about" "foo")
           (-replace-first 1 2 nil)
               ⇒ nil
 
  -- Function: -replace-last (old new list)
      Replace the last occurrence of OLD with NEW in LIST.
 
      Elements are compared using ‘equal’.
 
      See also: ‘-map-last’ (*note -map-last::)
 
           (-replace-last 1 "1" '(1 2 3 4 3 2 1))
               ⇒ (1 2 3 4 3 2 "1")
           (-replace-last "foo" "bar" '("a" "nice" "foo" "sentence" "about" "foo"))
               ⇒ ("a" "nice" "foo" "sentence" "about" "bar")
           (-replace-last 1 2 nil)
               ⇒ nil
 
  -- Function: -insert-at (n x list)
      Return a list with X inserted into LIST at position N.
 
      See also: ‘-splice’ (*note -splice::), ‘-splice-list’ (*note
      -splice-list::)
 
           (-insert-at 1 'x '(a b c))
               ⇒ (a x b c)
           (-insert-at 12 'x '(a b c))
               ⇒ (a b c x)
 
  -- Function: -replace-at (n x list)
      Return a list with element at Nth position in LIST replaced with X.
 
      See also: ‘-replace’ (*note -replace::)
 
           (-replace-at 0 9 '(0 1 2 3 4 5))
               ⇒ (9 1 2 3 4 5)
           (-replace-at 1 9 '(0 1 2 3 4 5))
               ⇒ (0 9 2 3 4 5)
           (-replace-at 4 9 '(0 1 2 3 4 5))
               ⇒ (0 1 2 3 9 5)
 
  -- Function: -update-at (n func list)
      Return a list with element at Nth position in LIST replaced with
      ‘(func (nth n list))‘.
 
      See also: ‘-map-when’ (*note -map-when::)
 
           (-update-at 0 (lambda (x) (+ x 9)) '(0 1 2 3 4 5))
               ⇒ (9 1 2 3 4 5)
           (-update-at 1 (lambda (x) (+ x 8)) '(0 1 2 3 4 5))
               ⇒ (0 9 2 3 4 5)
           (--update-at 2 (length it) '("foo" "bar" "baz" "quux"))
               ⇒ ("foo" "bar" 3 "quux")
 
  -- Function: -remove-at (n list)
      Return a list with element at Nth position in LIST removed.
 
      See also: ‘-remove-at-indices’ (*note -remove-at-indices::),
      ‘-remove’ (*note -remove::)
 
           (-remove-at 0 '("0" "1" "2" "3" "4" "5"))
               ⇒ ("1" "2" "3" "4" "5")
           (-remove-at 1 '("0" "1" "2" "3" "4" "5"))
               ⇒ ("0" "2" "3" "4" "5")
           (-remove-at 2 '("0" "1" "2" "3" "4" "5"))
               ⇒ ("0" "1" "3" "4" "5")
 
  -- Function: -remove-at-indices (indices list)
      Return a list whose elements are elements from LIST without
      elements selected as ‘(nth i list)‘ for all i from INDICES.
 
      See also: ‘-remove-at’ (*note -remove-at::), ‘-remove’ (*note
      -remove::)
 
           (-remove-at-indices '(0) '("0" "1" "2" "3" "4" "5"))
               ⇒ ("1" "2" "3" "4" "5")
           (-remove-at-indices '(0 2 4) '("0" "1" "2" "3" "4" "5"))
               ⇒ ("1" "3" "5")
           (-remove-at-indices '(0 5) '("0" "1" "2" "3" "4" "5"))
               ⇒ ("1" "2" "3" "4")
 
 
 File: dash.info,  Node: Reductions,  Next: Unfolding,  Prev: List to list,  Up: Functions
 
 2.4 Reductions
 ==============
 
 Functions reducing lists to a single value (which may also be a list).
 
  -- Function: -reduce-from (fn init list)
      Reduce the function FN across LIST, starting with INIT.  Return the
      result of applying FN to INIT and the first element of LIST, then
      applying FN to that result and the second element, etc.  If LIST is
      empty, return INIT without calling FN.
 
      This function’s anaphoric counterpart is ‘--reduce-from’.
 
      For other folds, see also ‘-reduce’ (*note -reduce::) and
      ‘-reduce-r’ (*note -reduce-r::).
 
           (-reduce-from #'- 10 '(1 2 3))
               ⇒ 4
           (-reduce-from #'list 10 '(1 2 3))
               ⇒ (((10 1) 2) 3)
           (--reduce-from (concat acc " " it) "START" '("a" "b" "c"))
               ⇒ "START a b c"
 
  -- Function: -reduce-r-from (fn init list)
      Reduce the function FN across LIST in reverse, starting with INIT.
      Return the result of applying FN to the last element of LIST and
      INIT, then applying FN to the second-to-last element and the
      previous result of FN, etc.  That is, the first argument of FN is
      the current element, and its second argument the accumulated value.
      If LIST is empty, return INIT without calling FN.
 
      This function is like ‘-reduce-from’ (*note -reduce-from::) but the
      operation associates from the right rather than left.  In other
      words, it starts from the end of LIST and flips the arguments to
      FN.  Conceptually, it is like replacing the conses in LIST with
      applications of FN, and its last link with INIT, and evaluating the
      resulting expression.
 
      This function’s anaphoric counterpart is ‘--reduce-r-from’.
 
      For other folds, see also ‘-reduce-r’ (*note -reduce-r::) and
      ‘-reduce’ (*note -reduce::).
 
           (-reduce-r-from #'- 10 '(1 2 3))
               ⇒ -8
           (-reduce-r-from #'list 10 '(1 2 3))
               ⇒ (1 (2 (3 10)))
           (--reduce-r-from (concat it " " acc) "END" '("a" "b" "c"))
               ⇒ "a b c END"
 
  -- Function: -reduce (fn list)
      Reduce the function FN across LIST.  Return the result of applying
      FN to the first two elements of LIST, then applying FN to that
      result and the third element, etc.  If LIST contains a single
      element, return it without calling FN.  If LIST is empty, return
      the result of calling FN with no arguments.
 
      This function’s anaphoric counterpart is ‘--reduce’.
 
      For other folds, see also ‘-reduce-from’ (*note -reduce-from::) and
      ‘-reduce-r’ (*note -reduce-r::).
 
           (-reduce #'- '(1 2 3 4))
               ⇒ -8
           (-reduce #'list '(1 2 3 4))
               ⇒ (((1 2) 3) 4)
           (--reduce (format "%s-%d" acc it) '(1 2 3))
               ⇒ "1-2-3"
 
  -- Function: -reduce-r (fn list)
      Reduce the function FN across LIST in reverse.  Return the result
      of applying FN to the last two elements of LIST, then applying FN
      to the third-to-last element and the previous result of FN, etc.
      That is, the first argument of FN is the current element, and its
      second argument the accumulated value.  If LIST contains a single
      element, return it without calling FN.  If LIST is empty, return
      the result of calling FN with no arguments.
 
      This function is like ‘-reduce’ (*note -reduce::) but the operation
      associates from the right rather than left.  In other words, it
      starts from the end of LIST and flips the arguments to FN.
      Conceptually, it is like replacing the conses in LIST with
      applications of FN, ignoring its last link, and evaluating the
      resulting expression.
 
      This function’s anaphoric counterpart is ‘--reduce-r’.
 
      For other folds, see also ‘-reduce-r-from’ (*note -reduce-r-from::)
      and ‘-reduce’ (*note -reduce::).
 
           (-reduce-r #'- '(1 2 3 4))
               ⇒ -2
           (-reduce-r #'list '(1 2 3 4))
               ⇒ (1 (2 (3 4)))
           (--reduce-r (format "%s-%d" acc it) '(1 2 3))
               ⇒ "3-2-1"
 
  -- Function: -reductions-from (fn init list)
      Return a list of FN’s intermediate reductions across LIST.  That
      is, a list of the intermediate values of the accumulator when
      ‘-reduce-from’ (*note -reduce-from::) (which see) is called with
      the same arguments.
 
      This function’s anaphoric counterpart is ‘--reductions-from’.
 
      For other folds, see also ‘-reductions’ (*note -reductions::) and
      ‘-reductions-r’ (*note -reductions-r::).
 
           (-reductions-from #'max 0 '(2 1 4 3))
               ⇒ (0 2 2 4 4)
           (-reductions-from #'* 1 '(1 2 3 4))
               ⇒ (1 1 2 6 24)
           (--reductions-from (format "(FN %s %d)" acc it) "INIT" '(1 2 3))
               ⇒ ("INIT" "(FN INIT 1)" "(FN (FN INIT 1) 2)" "(FN (FN (FN INIT 1) 2) 3)")
 
  -- Function: -reductions-r-from (fn init list)
      Return a list of FN’s intermediate reductions across reversed LIST.
      That is, a list of the intermediate values of the accumulator when
      ‘-reduce-r-from’ (*note -reduce-r-from::) (which see) is called
      with the same arguments.
 
      This function’s anaphoric counterpart is ‘--reductions-r-from’.
 
      For other folds, see also ‘-reductions’ (*note -reductions::) and
      ‘-reductions-r’ (*note -reductions-r::).
 
           (-reductions-r-from #'max 0 '(2 1 4 3))
               ⇒ (4 4 4 3 0)
           (-reductions-r-from #'* 1 '(1 2 3 4))
               ⇒ (24 24 12 4 1)
           (--reductions-r-from (format "(FN %d %s)" it acc) "INIT" '(1 2 3))
               ⇒ ("(FN 1 (FN 2 (FN 3 INIT)))" "(FN 2 (FN 3 INIT))" "(FN 3 INIT)" "INIT")
 
  -- Function: -reductions (fn list)
      Return a list of FN’s intermediate reductions across LIST.  That
      is, a list of the intermediate values of the accumulator when
      ‘-reduce’ (*note -reduce::) (which see) is called with the same
      arguments.
 
      This function’s anaphoric counterpart is ‘--reductions’.
 
      For other folds, see also ‘-reductions’ (*note -reductions::) and
      ‘-reductions-r’ (*note -reductions-r::).
 
           (-reductions #'+ '(1 2 3 4))
               ⇒ (1 3 6 10)
           (-reductions #'* '(1 2 3 4))
               ⇒ (1 2 6 24)
           (--reductions (format "(FN %s %d)" acc it) '(1 2 3))
               ⇒ (1 "(FN 1 2)" "(FN (FN 1 2) 3)")
 
  -- Function: -reductions-r (fn list)
      Return a list of FN’s intermediate reductions across reversed LIST.
      That is, a list of the intermediate values of the accumulator when
      ‘-reduce-r’ (*note -reduce-r::) (which see) is called with the same
      arguments.
 
      This function’s anaphoric counterpart is ‘--reductions-r’.
 
      For other folds, see also ‘-reductions-r-from’ (*note
      -reductions-r-from::) and ‘-reductions’ (*note -reductions::).
 
           (-reductions-r #'+ '(1 2 3 4))
               ⇒ (10 9 7 4)
           (-reductions-r #'* '(1 2 3 4))
               ⇒ (24 24 12 4)
           (--reductions-r (format "(FN %d %s)" it acc) '(1 2 3))
               ⇒ ("(FN 1 (FN 2 3))" "(FN 2 3)" 3)
 
  -- Function: -count (pred list)
      Counts the number of items in LIST where (PRED item) is non-nil.
 
           (-count 'even? '(1 2 3 4 5))
               ⇒ 2
           (--count (< it 4) '(1 2 3 4))
               ⇒ 3
 
  -- Function: -sum (list)
      Return the sum of LIST.
 
           (-sum ())
               ⇒ 0
           (-sum '(1))
               ⇒ 1
           (-sum '(1 2 3 4))
               ⇒ 10
 
  -- Function: -running-sum (list)
      Return a list with running sums of items in LIST.  LIST must be
      non-empty.
 
           (-running-sum '(1 2 3 4))
               ⇒ (1 3 6 10)
           (-running-sum '(1))
               ⇒ (1)
           (-running-sum ())
               error→ Wrong type argument: consp, nil
 
  -- Function: -product (list)
      Return the product of LIST.
 
           (-product ())
               ⇒ 1
           (-product '(1))
               ⇒ 1
           (-product '(1 2 3 4))
               ⇒ 24
 
  -- Function: -running-product (list)
      Return a list with running products of items in LIST.  LIST must be
      non-empty.
 
           (-running-product '(1 2 3 4))
               ⇒ (1 2 6 24)
           (-running-product '(1))
               ⇒ (1)
           (-running-product ())
               error→ Wrong type argument: consp, nil
 
  -- Function: -inits (list)
      Return all prefixes of LIST.
 
           (-inits '(1 2 3 4))
               ⇒ (nil (1) (1 2) (1 2 3) (1 2 3 4))
           (-inits nil)
               ⇒ (nil)
           (-inits '(1))
               ⇒ (nil (1))
 
  -- Function: -tails (list)
      Return all suffixes of LIST
 
           (-tails '(1 2 3 4))
               ⇒ ((1 2 3 4) (2 3 4) (3 4) (4) nil)
           (-tails nil)
               ⇒ (nil)
           (-tails '(1))
               ⇒ ((1) nil)
 
  -- Function: -common-prefix (&rest lists)
      Return the longest common prefix of LISTS.
 
           (-common-prefix '(1))
               ⇒ (1)
           (-common-prefix '(1 2) '(3 4) '(1 2))
               ⇒ ()
           (-common-prefix '(1 2) '(1 2 3) '(1 2 3 4))
               ⇒ (1 2)
 
  -- Function: -common-suffix (&rest lists)
      Return the longest common suffix of LISTS.
 
           (-common-suffix '(1))
               ⇒ (1)
           (-common-suffix '(1 2) '(3 4) '(1 2))
               ⇒ ()
           (-common-suffix '(1 2 3 4) '(2 3 4) '(3 4))
               ⇒ (3 4)
 
  -- Function: -min (list)
      Return the smallest value from LIST of numbers or markers.
 
           (-min '(0))
               ⇒ 0
           (-min '(3 2 1))
               ⇒ 1
           (-min '(1 2 3))
               ⇒ 1
 
  -- Function: -min-by (comparator list)
      Take a comparison function COMPARATOR and a LIST and return the
      least element of the list by the comparison function.
 
      See also combinator ‘-on’ (*note -on::) which can transform the
      values before comparing them.
 
           (-min-by '> '(4 3 6 1))
               ⇒ 1
           (--min-by (> (car it) (car other)) '((1 2 3) (2) (3 2)))
               ⇒ (1 2 3)
           (--min-by (> (length it) (length other)) '((1 2 3) (2) (3 2)))
               ⇒ (2)
 
  -- Function: -max (list)
      Return the largest value from LIST of numbers or markers.
 
           (-max '(0))
               ⇒ 0
           (-max '(3 2 1))
               ⇒ 3
           (-max '(1 2 3))
               ⇒ 3
 
  -- Function: -max-by (comparator list)
      Take a comparison function COMPARATOR and a LIST and return the
      greatest element of the list by the comparison function.
 
      See also combinator ‘-on’ (*note -on::) which can transform the
      values before comparing them.
 
           (-max-by '> '(4 3 6 1))
               ⇒ 6
           (--max-by (> (car it) (car other)) '((1 2 3) (2) (3 2)))
               ⇒ (3 2)
           (--max-by (> (length it) (length other)) '((1 2 3) (2) (3 2)))
               ⇒ (1 2 3)
 
 
 File: dash.info,  Node: Unfolding,  Next: Predicates,  Prev: Reductions,  Up: Functions
 
 2.5 Unfolding
 =============
 
 Operations dual to reductions, building lists from a seed value rather
 than consuming a list to produce a single value.
 
  -- Function: -iterate (fun init n)
      Return a list of iterated applications of FUN to INIT.
 
      This means a list of the form:
 
      (INIT (FUN INIT) (FUN (FUN INIT)) ...)
 
      N is the length of the returned list.
 
           (-iterate #'1+ 1 10)
               ⇒ (1 2 3 4 5 6 7 8 9 10)
           (-iterate (lambda (x) (+ x x)) 2 5)
               ⇒ (2 4 8 16 32)
           (--iterate (* it it) 2 5)
               ⇒ (2 4 16 256 65536)
 
  -- Function: -unfold (fun seed)
      Build a list from SEED using FUN.
 
      This is "dual" operation to ‘-reduce-r’ (*note -reduce-r::): while
      -reduce-r consumes a list to produce a single value, ‘-unfold’
      (*note -unfold::) takes a seed value and builds a (potentially
      infinite!)  list.
 
      FUN should return ‘nil’ to stop the generating process, or a cons
      (A .  B), where A will be prepended to the result and B is the new
      seed.
 
           (-unfold (lambda (x) (unless (= x 0) (cons x (1- x)))) 10)
               ⇒ (10 9 8 7 6 5 4 3 2 1)
           (--unfold (when it (cons it (cdr it))) '(1 2 3 4))
               ⇒ ((1 2 3 4) (2 3 4) (3 4) (4))
           (--unfold (when it (cons it (butlast it))) '(1 2 3 4))
               ⇒ ((1 2 3 4) (1 2 3) (1 2) (1))
 
 
 File: dash.info,  Node: Predicates,  Next: Partitioning,  Prev: Unfolding,  Up: Functions
 
 2.6 Predicates
 ==============
 
 Reductions of one or more lists to a boolean value.
 
  -- Function: -some (pred list)
      Return (PRED x) for the first LIST item where (PRED x) is non-nil,
      else nil.
 
      Alias: ‘-any’.
 
      This function’s anaphoric counterpart is ‘--some’.
 
           (-some #'stringp '(1 "2" 3))
               ⇒ t
           (--some (string-match-p "x" it) '("foo" "axe" "xor"))
               ⇒ 1
           (--some (= it-index 3) '(0 1 2))
               ⇒ nil
 
  -- Function: -every (pred list)
      Return non-nil if PRED returns non-nil for all items in LIST.  If
      so, return the last such result of PRED.  Otherwise, once an item
      is reached for which PRED returns nil, return nil without calling
      PRED on any further LIST elements.
 
      This function is like ‘-every-p’, but on success returns the last
      non-nil result of PRED instead of just t.
 
      This function’s anaphoric counterpart is ‘--every’.
 
           (-every #'numberp '(1 2 3))
               ⇒ t
           (--every (string-match-p "x" it) '("axe" "xor"))
               ⇒ 0
           (--every (= it it-index) '(0 1 3))
               ⇒ nil
 
  -- Function: -any? (pred list)
      Return t if (PRED x) is non-nil for any x in LIST, else nil.
 
      Alias: ‘-any-p’, ‘-some?’, ‘-some-p’
 
           (-any? #'numberp '(nil 0 t))
               ⇒ t
           (-any? #'numberp '(nil t t))
               ⇒ nil
           (-any? #'null '(1 3 5))
               ⇒ nil
 
  -- Function: -all? (pred list)
      Return t if (PRED X) is non-nil for all X in LIST, else nil.  In
      the latter case, stop after the first X for which (PRED X) is nil,
      without calling PRED on any subsequent elements of LIST.
 
      The similar function ‘-every’ (*note -every::) is more widely
      useful, since it returns the last non-nil result of PRED instead of
      just t on success.
 
      Alias: ‘-all-p’, ‘-every-p’, ‘-every?’.
 
      This function’s anaphoric counterpart is ‘--all?’.
 
           (-all? #'numberp '(1 2 3))
               ⇒ t
           (-all? #'numberp '(2 t 6))
               ⇒ nil
           (--all? (= 0 (% it 2)) '(2 4 6))
               ⇒ t
 
  -- Function: -none? (pred list)
      Return t if (PRED x) is nil for all x in LIST, else nil.
 
      Alias: ‘-none-p’
 
           (-none? 'even? '(1 2 3))
               ⇒ nil
           (-none? 'even? '(1 3 5))
               ⇒ t
           (--none? (= 0 (% it 2)) '(1 2 3))
               ⇒ nil
 
  -- Function: -only-some? (pred list)
      Return ‘t‘ if at least one item of LIST matches PRED and at least
      one item of LIST does not match PRED.  Return ‘nil‘ both if all
      items match the predicate or if none of the items match the
      predicate.
 
      Alias: ‘-only-some-p’
 
           (-only-some? 'even? '(1 2 3))
               ⇒ t
           (-only-some? 'even? '(1 3 5))
               ⇒ nil
           (-only-some? 'even? '(2 4 6))
               ⇒ nil
 
  -- Function: -contains? (list element)
      Return non-nil if LIST contains ELEMENT.
 
      The test for equality is done with ‘equal’, or with ‘-compare-fn’
      if that’s non-nil.
 
      Alias: ‘-contains-p’
 
           (-contains? '(1 2 3) 1)
               ⇒ t
           (-contains? '(1 2 3) 2)
               ⇒ t
           (-contains? '(1 2 3) 4)
               ⇒ nil
 
  -- Function: -same-items? (list list2)
      Return true if LIST and LIST2 has the same items.
 
      The order of the elements in the lists does not matter.
 
      Alias: ‘-same-items-p’
 
           (-same-items? '(1 2 3) '(1 2 3))
               ⇒ t
           (-same-items? '(1 2 3) '(3 2 1))
               ⇒ t
           (-same-items? '(1 2 3) '(1 2 3 4))
               ⇒ nil
 
  -- Function: -is-prefix? (prefix list)
      Return non-nil if PREFIX is a prefix of LIST.
 
      Alias: ‘-is-prefix-p’.
 
           (-is-prefix? '(1 2 3) '(1 2 3 4 5))
               ⇒ t
           (-is-prefix? '(1 2 3 4 5) '(1 2 3))
               ⇒ nil
           (-is-prefix? '(1 3) '(1 2 3 4 5))
               ⇒ nil
 
  -- Function: -is-suffix? (suffix list)
      Return non-nil if SUFFIX is a suffix of LIST.
 
      Alias: ‘-is-suffix-p’.
 
           (-is-suffix? '(3 4 5) '(1 2 3 4 5))
               ⇒ t
           (-is-suffix? '(1 2 3 4 5) '(3 4 5))
               ⇒ nil
           (-is-suffix? '(3 5) '(1 2 3 4 5))
               ⇒ nil
 
  -- Function: -is-infix? (infix list)
      Return non-nil if INFIX is infix of LIST.
 
      This operation runs in O(n^2) time
 
      Alias: ‘-is-infix-p’
 
           (-is-infix? '(1 2 3) '(1 2 3 4 5))
               ⇒ t
           (-is-infix? '(2 3 4) '(1 2 3 4 5))
               ⇒ t
           (-is-infix? '(3 4 5) '(1 2 3 4 5))
               ⇒ t
 
  -- Function: -cons-pair? (obj)
      Return non-nil if OBJ is a true cons pair.  That is, a cons (A .
      B) where B is not a list.
 
      Alias: ‘-cons-pair-p’.
 
           (-cons-pair? '(1 . 2))
               ⇒ t
           (-cons-pair? '(1 2))
               ⇒ nil
           (-cons-pair? '(1))
               ⇒ nil
 
 
 File: dash.info,  Node: Partitioning,  Next: Indexing,  Prev: Predicates,  Up: Functions
 
 2.7 Partitioning
 ================
 
 Functions partitioning the input list into a list of lists.
 
  -- Function: -split-at (n list)
      Split LIST into two sublists after the Nth element.  The result is
      a list of two elements (TAKE DROP) where TAKE is a new list of the
      first N elements of LIST, and DROP is the remaining elements of
      LIST (not a copy).  TAKE and DROP are like the results of ‘-take’
      (*note -take::) and ‘-drop’ (*note -drop::), respectively, but the
      split is done in a single list traversal.
 
           (-split-at 3 '(1 2 3 4 5))
               ⇒ ((1 2 3) (4 5))
           (-split-at 17 '(1 2 3 4 5))
               ⇒ ((1 2 3 4 5) nil)
           (-split-at 0 '(1 2 3 4 5))
               ⇒ (nil (1 2 3 4 5))
 
  -- Function: -split-with (pred list)
      Return a list of ((-take-while PRED LIST) (-drop-while PRED LIST)),
      in no more than one pass through the list.
 
           (-split-with 'even? '(1 2 3 4))
               ⇒ (nil (1 2 3 4))
           (-split-with 'even? '(2 4 5 6))
               ⇒ ((2 4) (5 6))
           (--split-with (< it 4) '(1 2 3 4 3 2 1))
               ⇒ ((1 2 3) (4 3 2 1))
 
  -- Macro: -split-on (item list)
      Split the LIST each time ITEM is found.
 
      Unlike ‘-partition-by’ (*note -partition-by::), the ITEM is
      discarded from the results.  Empty lists are also removed from the
      result.
 
      Comparison is done by ‘equal’.
 
      See also ‘-split-when’ (*note -split-when::)
 
           (-split-on '| '(Nil | Leaf a | Node [Tree a]))
               ⇒ ((Nil) (Leaf a) (Node [Tree a]))
           (-split-on :endgroup '("a" "b" :endgroup "c" :endgroup "d" "e"))
               ⇒ (("a" "b") ("c") ("d" "e"))
           (-split-on :endgroup '("a" "b" :endgroup :endgroup "d" "e"))
               ⇒ (("a" "b") ("d" "e"))
 
  -- Function: -split-when (fn list)
      Split the LIST on each element where FN returns non-nil.
 
      Unlike ‘-partition-by’ (*note -partition-by::), the "matched"
      element is discarded from the results.  Empty lists are also
      removed from the result.
 
      This function can be thought of as a generalization of
      ‘split-string’.
 
           (-split-when 'even? '(1 2 3 4 5 6))
               ⇒ ((1) (3) (5))
           (-split-when 'even? '(1 2 3 4 6 8 9))
               ⇒ ((1) (3) (9))
           (--split-when (memq it '(&optional &rest)) '(a b &optional c d &rest args))
               ⇒ ((a b) (c d) (args))
 
  -- Function: -separate (pred list)
      Return a list of ((-filter PRED LIST) (-remove PRED LIST)), in one
      pass through the list.
 
           (-separate (lambda (num) (= 0 (% num 2))) '(1 2 3 4 5 6 7))
               ⇒ ((2 4 6) (1 3 5 7))
           (--separate (< it 5) '(3 7 5 9 3 2 1 4 6))
               ⇒ ((3 3 2 1 4) (7 5 9 6))
           (-separate 'cdr '((1 2) (1) (1 2 3) (4)))
               ⇒ (((1 2) (1 2 3)) ((1) (4)))
 
  -- Function: -partition (n list)
      Return a new list with the items in LIST grouped into N-sized
      sublists.  If there are not enough items to make the last group
      N-sized, those items are discarded.
 
           (-partition 2 '(1 2 3 4 5 6))
               ⇒ ((1 2) (3 4) (5 6))
           (-partition 2 '(1 2 3 4 5 6 7))
               ⇒ ((1 2) (3 4) (5 6))
           (-partition 3 '(1 2 3 4 5 6 7))
               ⇒ ((1 2 3) (4 5 6))
 
  -- Function: -partition-all (n list)
      Return a new list with the items in LIST grouped into N-sized
      sublists.  The last group may contain less than N items.
 
           (-partition-all 2 '(1 2 3 4 5 6))
               ⇒ ((1 2) (3 4) (5 6))
           (-partition-all 2 '(1 2 3 4 5 6 7))
               ⇒ ((1 2) (3 4) (5 6) (7))
           (-partition-all 3 '(1 2 3 4 5 6 7))
               ⇒ ((1 2 3) (4 5 6) (7))
 
  -- Function: -partition-in-steps (n step list)
      Return a new list with the items in LIST grouped into N-sized
      sublists at offsets STEP apart.  If there are not enough items to
      make the last group N-sized, those items are discarded.
 
           (-partition-in-steps 2 1 '(1 2 3 4))
               ⇒ ((1 2) (2 3) (3 4))
           (-partition-in-steps 3 2 '(1 2 3 4))
               ⇒ ((1 2 3))
           (-partition-in-steps 3 2 '(1 2 3 4 5))
               ⇒ ((1 2 3) (3 4 5))
 
  -- Function: -partition-all-in-steps (n step list)
      Return a new list with the items in LIST grouped into N-sized
      sublists at offsets STEP apart.  The last groups may contain less
      than N items.
 
           (-partition-all-in-steps 2 1 '(1 2 3 4))
               ⇒ ((1 2) (2 3) (3 4) (4))
           (-partition-all-in-steps 3 2 '(1 2 3 4))
               ⇒ ((1 2 3) (3 4))
           (-partition-all-in-steps 3 2 '(1 2 3 4 5))
               ⇒ ((1 2 3) (3 4 5) (5))
 
  -- Function: -partition-by (fn list)
      Apply FN to each item in LIST, splitting it each time FN returns a
      new value.
 
           (-partition-by 'even? ())
               ⇒ ()
           (-partition-by 'even? '(1 1 2 2 2 3 4 6 8))
               ⇒ ((1 1) (2 2 2) (3) (4 6 8))
           (--partition-by (< it 3) '(1 2 3 4 3 2 1))
               ⇒ ((1 2) (3 4 3) (2 1))
 
  -- Function: -partition-by-header (fn list)
      Apply FN to the first item in LIST.  That is the header value.
      Apply FN to each item in LIST, splitting it each time FN returns
      the header value, but only after seeing at least one other value
      (the body).
 
           (--partition-by-header (= it 1) '(1 2 3 1 2 1 2 3 4))
               ⇒ ((1 2 3) (1 2) (1 2 3 4))
           (--partition-by-header (> it 0) '(1 2 0 1 0 1 2 3 0))
               ⇒ ((1 2 0) (1 0) (1 2 3 0))
           (-partition-by-header 'even? '(2 1 1 1 4 1 3 5 6 6 1))
               ⇒ ((2 1 1 1) (4 1 3 5) (6 6 1))
 
  -- Function: -partition-after-pred (pred list)
      Partition LIST after each element for which PRED returns non-nil.
 
      This function’s anaphoric counterpart is ‘--partition-after-pred’.
 
           (-partition-after-pred #'booleanp ())
               ⇒ ()
           (-partition-after-pred #'booleanp '(t t))
               ⇒ ((t) (t))
           (-partition-after-pred #'booleanp '(0 0 t t 0 t))
               ⇒ ((0 0 t) (t) (0 t))
 
  -- Function: -partition-before-pred (pred list)
      Partition directly before each time PRED is true on an element of
      LIST.
 
           (-partition-before-pred #'booleanp ())
               ⇒ ()
           (-partition-before-pred #'booleanp '(0 t))
               ⇒ ((0) (t))
           (-partition-before-pred #'booleanp '(0 0 t 0 t t))
               ⇒ ((0 0) (t 0) (t) (t))
 
  -- Function: -partition-before-item (item list)
      Partition directly before each time ITEM appears in LIST.
 
           (-partition-before-item 3 ())
               ⇒ ()
           (-partition-before-item 3 '(1))
               ⇒ ((1))
           (-partition-before-item 3 '(3))
               ⇒ ((3))
 
  -- Function: -partition-after-item (item list)
      Partition directly after each time ITEM appears in LIST.
 
           (-partition-after-item 3 ())
               ⇒ ()
           (-partition-after-item 3 '(1))
               ⇒ ((1))
           (-partition-after-item 3 '(3))
               ⇒ ((3))
 
  -- Function: -group-by (fn list)
      Separate LIST into an alist whose keys are FN applied to the
      elements of LIST.  Keys are compared by ‘equal’.
 
           (-group-by 'even? ())
               ⇒ ()
           (-group-by 'even? '(1 1 2 2 2 3 4 6 8))
               ⇒ ((nil 1 1 3) (t 2 2 2 4 6 8))
           (--group-by (car (split-string it "/")) '("a/b" "c/d" "a/e"))
               ⇒ (("a" "a/b" "a/e") ("c" "c/d"))
 
 
 File: dash.info,  Node: Indexing,  Next: Set operations,  Prev: Partitioning,  Up: Functions
 
 2.8 Indexing
 ============
 
 Functions retrieving or sorting based on list indices and related
 predicates.
 
  -- Function: -elem-index (elem list)
      Return the index of the first element in the given LIST which is
      equal to the query element ELEM, or nil if there is no such
      element.
 
           (-elem-index 2 '(6 7 8 2 3 4))
               ⇒ 3
           (-elem-index "bar" '("foo" "bar" "baz"))
               ⇒ 1
           (-elem-index '(1 2) '((3) (5 6) (1 2) nil))
               ⇒ 2
 
  -- Function: -elem-indices (elem list)
      Return the indices of all elements in LIST equal to the query
      element ELEM, in ascending order.
 
           (-elem-indices 2 '(6 7 8 2 3 4 2 1))
               ⇒ (3 6)
           (-elem-indices "bar" '("foo" "bar" "baz"))
               ⇒ (1)
           (-elem-indices '(1 2) '((3) (1 2) (5 6) (1 2) nil))
               ⇒ (1 3)
 
  -- Function: -find-index (pred list)
      Take a predicate PRED and a LIST and return the index of the first
      element in the list satisfying the predicate, or nil if there is no
      such element.
 
      See also ‘-first’ (*note -first::).
 
           (-find-index 'even? '(2 4 1 6 3 3 5 8))
               ⇒ 0
           (--find-index (< 5 it) '(2 4 1 6 3 3 5 8))
               ⇒ 3
           (-find-index (-partial 'string-lessp "baz") '("bar" "foo" "baz"))
               ⇒ 1
 
  -- Function: -find-last-index (pred list)
      Take a predicate PRED and a LIST and return the index of the last
      element in the list satisfying the predicate, or nil if there is no
      such element.
 
      See also ‘-last’ (*note -last::).
 
           (-find-last-index 'even? '(2 4 1 6 3 3 5 8))
               ⇒ 7
           (--find-last-index (< 5 it) '(2 7 1 6 3 8 5 2))
               ⇒ 5
           (-find-last-index (-partial 'string-lessp "baz") '("q" "foo" "baz"))
               ⇒ 1
 
  -- Function: -find-indices (pred list)
      Return the indices of all elements in LIST satisfying the predicate
      PRED, in ascending order.
 
           (-find-indices 'even? '(2 4 1 6 3 3 5 8))
               ⇒ (0 1 3 7)
           (--find-indices (< 5 it) '(2 4 1 6 3 3 5 8))
               ⇒ (3 7)
           (-find-indices (-partial 'string-lessp "baz") '("bar" "foo" "baz"))
               ⇒ (1)
 
  -- Function: -grade-up (comparator list)
      Grade elements of LIST using COMPARATOR relation.  This yields a
      permutation vector such that applying this permutation to LIST
      sorts it in ascending order.
 
           (-grade-up #'< '(3 1 4 2 1 3 3))
               ⇒ (1 4 3 0 5 6 2)
           (let ((l '(3 1 4 2 1 3 3))) (-select-by-indices (-grade-up #'< l) l))
               ⇒ (1 1 2 3 3 3 4)
 
  -- Function: -grade-down (comparator list)
      Grade elements of LIST using COMPARATOR relation.  This yields a
      permutation vector such that applying this permutation to LIST
      sorts it in descending order.
 
           (-grade-down #'< '(3 1 4 2 1 3 3))
               ⇒ (2 0 5 6 3 1 4)
           (let ((l '(3 1 4 2 1 3 3))) (-select-by-indices (-grade-down #'< l) l))
               ⇒ (4 3 3 3 2 1 1)
 
 
 File: dash.info,  Node: Set operations,  Next: Other list operations,  Prev: Indexing,  Up: Functions
 
 2.9 Set operations
 ==================
 
 Operations pretending lists are sets.
 
  -- Function: -union (list list2)
      Return a new list containing the elements of LIST and elements of
      LIST2 that are not in LIST.  The test for equality is done with
      ‘equal’, or with ‘-compare-fn’ if that’s non-nil.
 
           (-union '(1 2 3) '(3 4 5))
               ⇒ (1 2 3 4 5)
           (-union '(1 2 3 4) ())
               ⇒ (1 2 3 4)
           (-union '(1 1 2 2) '(3 2 1))
               ⇒ (1 1 2 2 3)
 
  -- Function: -difference (list list2)
      Return a new list with only the members of LIST that are not in
      LIST2.  The test for equality is done with ‘equal’, or with
      ‘-compare-fn’ if that’s non-nil.
 
           (-difference () ())
               ⇒ ()
           (-difference '(1 2 3) '(4 5 6))
               ⇒ (1 2 3)
           (-difference '(1 2 3 4) '(3 4 5 6))
               ⇒ (1 2)
 
  -- Function: -intersection (list list2)
      Return a new list containing only the elements that are members of
      both LIST and LIST2.  The test for equality is done with ‘equal’,
      or with ‘-compare-fn’ if that’s non-nil.
 
           (-intersection () ())
               ⇒ ()
           (-intersection '(1 2 3) '(4 5 6))
               ⇒ ()
           (-intersection '(1 2 3 4) '(3 4 5 6))
               ⇒ (3 4)
 
  -- Function: -powerset (list)
      Return the power set of LIST.
 
           (-powerset ())
               ⇒ (nil)
           (-powerset '(x y z))
               ⇒ ((x y z) (x y) (x z) (x) (y z) (y) (z) nil)
 
  -- Function: -permutations (list)
      Return the permutations of LIST.
 
           (-permutations ())
               ⇒ (nil)
           (-permutations '(1 2))
               ⇒ ((1 2) (2 1))
           (-permutations '(a b c))
               ⇒ ((a b c) (a c b) (b a c) (b c a) (c a b) (c b a))
 
  -- Function: -distinct (list)
      Return a new list with all duplicates removed.  The test for
      equality is done with ‘equal’, or with ‘-compare-fn’ if that’s
      non-nil.
 
      Alias: ‘-uniq’
 
           (-distinct ())
               ⇒ ()
           (-distinct '(1 2 2 4))
               ⇒ (1 2 4)
           (-distinct '(t t t))
               ⇒ (t)
 
 
 File: dash.info,  Node: Other list operations,  Next: Tree operations,  Prev: Set operations,  Up: Functions
 
 2.10 Other list operations
 ==========================
 
 Other list functions not fit to be classified elsewhere.
 
  -- Function: -rotate (n list)
      Rotate LIST N places to the right (left if N is negative).  The
      time complexity is O(n).
 
           (-rotate 3 '(1 2 3 4 5 6 7))
               ⇒ (5 6 7 1 2 3 4)
           (-rotate -3 '(1 2 3 4 5 6 7))
               ⇒ (4 5 6 7 1 2 3)
           (-rotate 16 '(1 2 3 4 5 6 7))
               ⇒ (6 7 1 2 3 4 5)
 
  -- Function: -repeat (n x)
      Return a new list of length N with each element being X.  Return
      nil if N is less than 1.
 
           (-repeat 3 :a)
               ⇒ (:a :a :a)
           (-repeat 1 :a)
               ⇒ (:a)
           (-repeat 0 :a)
               ⇒ nil
 
  -- Function: -cons* (&rest args)
      Make a new list from the elements of ARGS.  The last 2 elements of
      ARGS are used as the final cons of the result, so if the final
      element of ARGS is not a list, the result is a dotted list.  With
      no ARGS, return nil.
 
           (-cons* 1 2)
               ⇒ (1 . 2)
           (-cons* 1 2 3)
               ⇒ (1 2 . 3)
           (-cons* 1)
               ⇒ 1
 
  -- Function: -snoc (list elem &rest elements)
      Append ELEM to the end of the list.
 
      This is like ‘cons’, but operates on the end of list.
 
      If ELEMENTS is non nil, append these to the list as well.
 
           (-snoc '(1 2 3) 4)
               ⇒ (1 2 3 4)
           (-snoc '(1 2 3) 4 5 6)
               ⇒ (1 2 3 4 5 6)
           (-snoc '(1 2 3) '(4 5 6))
               ⇒ (1 2 3 (4 5 6))
 
  -- Function: -interpose (sep list)
      Return a new list of all elements in LIST separated by SEP.
 
           (-interpose "-" ())
               ⇒ ()
           (-interpose "-" '("a"))
               ⇒ ("a")
           (-interpose "-" '("a" "b" "c"))
               ⇒ ("a" "-" "b" "-" "c")
 
  -- Function: -interleave (&rest lists)
      Return a new list of the first item in each list, then the second
      etc.
 
           (-interleave '(1 2) '("a" "b"))
               ⇒ (1 "a" 2 "b")
           (-interleave '(1 2) '("a" "b") '("A" "B"))
               ⇒ (1 "a" "A" 2 "b" "B")
           (-interleave '(1 2 3) '("a" "b"))
               ⇒ (1 "a" 2 "b")
 
  -- Function: -iota (count &optional start step)
      Return a list containing COUNT numbers.  Starts from START and adds
      STEP each time.  The default START is zero, the default STEP is 1.
      This function takes its name from the corresponding primitive in
      the APL language.
 
           (-iota 6)
               ⇒ (0 1 2 3 4 5)
           (-iota 4 2.5 -2)
               ⇒ (2.5 0.5 -1.5 -3.5)
           (-iota -1)
               error→ Wrong type argument: natnump, -1
 
  -- Function: -zip-with (fn list1 list2)
      Zip the two lists LIST1 and LIST2 using a function FN.  This
      function is applied pairwise taking as first argument element of
      LIST1 and as second argument element of LIST2 at corresponding
      position.
 
      The anaphoric form ‘--zip-with’ binds the elements from LIST1 as
      symbol ‘it’, and the elements from LIST2 as symbol ‘other’.
 
           (-zip-with '+ '(1 2 3) '(4 5 6))
               ⇒ (5 7 9)
           (-zip-with 'cons '(1 2 3) '(4 5 6))
               ⇒ ((1 . 4) (2 . 5) (3 . 6))
           (--zip-with (concat it " and " other) '("Batman" "Jekyll") '("Robin" "Hyde"))
               ⇒ ("Batman and Robin" "Jekyll and Hyde")
 
  -- Function: -zip (&rest lists)
      Zip LISTS together.  Group the head of each list, followed by the
      second elements of each list, and so on.  The lengths of the
      returned groupings are equal to the length of the shortest input
      list.
 
      If two lists are provided as arguments, return the groupings as a
      list of cons cells.  Otherwise, return the groupings as a list of
      lists.
 
      Use ‘-zip-lists’ (*note -zip-lists::) if you need the return value
      to always be a list of lists.
 
      Alias: ‘-zip-pair’
 
      See also: ‘-zip-lists’ (*note -zip-lists::)
 
           (-zip '(1 2 3) '(4 5 6))
               ⇒ ((1 . 4) (2 . 5) (3 . 6))
           (-zip '(1 2 3) '(4 5 6 7))
               ⇒ ((1 . 4) (2 . 5) (3 . 6))
           (-zip '(1 2) '(3 4 5) '(6))
               ⇒ ((1 3 6))
 
  -- Function: -zip-lists (&rest lists)
      Zip LISTS together.  Group the head of each list, followed by the
      second elements of each list, and so on.  The lengths of the
      returned groupings are equal to the length of the shortest input
      list.
 
      The return value is always list of lists, which is a difference
      from ‘-zip-pair’ which returns a cons-cell in case two input lists
      are provided.
 
      See also: ‘-zip’ (*note -zip::)
 
           (-zip-lists '(1 2 3) '(4 5 6))
               ⇒ ((1 4) (2 5) (3 6))
           (-zip-lists '(1 2 3) '(4 5 6 7))
               ⇒ ((1 4) (2 5) (3 6))
           (-zip-lists '(1 2) '(3 4 5) '(6))
               ⇒ ((1 3 6))
 
  -- Function: -zip-fill (fill-value &rest lists)
      Zip LISTS, with FILL-VALUE padded onto the shorter lists.  The
      lengths of the returned groupings are equal to the length of the
      longest input list.
 
           (-zip-fill 0 '(1 2 3 4 5) '(6 7 8 9))
               ⇒ ((1 . 6) (2 . 7) (3 . 8) (4 . 9) (5 . 0))
 
  -- Function: -unzip (lists)
      Unzip LISTS.
 
      This works just like ‘-zip’ (*note -zip::) but takes a list of
      lists instead of a variable number of arguments, such that
 
      (-unzip (-zip L1 L2 L3 ...))
 
      is identity (given that the lists are the same length).
 
      Note in particular that calling this on a list of two lists will
      return a list of cons-cells such that the above identity works.
 
      See also: ‘-zip’ (*note -zip::)
 
           (-unzip (-zip '(1 2 3) '(a b c) '("e" "f" "g")))
               ⇒ ((1 2 3) (a b c) ("e" "f" "g"))
           (-unzip '((1 2) (3 4) (5 6) (7 8) (9 10)))
               ⇒ ((1 3 5 7 9) (2 4 6 8 10))
           (-unzip '((1 2) (3 4)))
               ⇒ ((1 . 3) (2 . 4))
 
  -- Function: -cycle (list)
      Return an infinite circular copy of LIST.  The returned list cycles
      through the elements of LIST and repeats from the beginning.
 
           (-take 5 (-cycle '(1 2 3)))
               ⇒ (1 2 3 1 2)
           (-take 7 (-cycle '(1 "and" 3)))
               ⇒ (1 "and" 3 1 "and" 3 1)
           (-zip (-cycle '(1 2 3)) '(1 2))
               ⇒ ((1 . 1) (2 . 2))
 
  -- Function: -pad (fill-value &rest lists)
      Appends FILL-VALUE to the end of each list in LISTS such that they
      will all have the same length.
 
           (-pad 0 ())
               ⇒ (nil)
           (-pad 0 '(1))
               ⇒ ((1))
           (-pad 0 '(1 2 3) '(4 5))
               ⇒ ((1 2 3) (4 5 0))
 
  -- Function: -table (fn &rest lists)
      Compute outer product of LISTS using function FN.
 
      The function FN should have the same arity as the number of
      supplied lists.
 
      The outer product is computed by applying fn to all possible
      combinations created by taking one element from each list in order.
      The dimension of the result is (length lists).
 
      See also: ‘-table-flat’ (*note -table-flat::)
 
           (-table '* '(1 2 3) '(1 2 3))
               ⇒ ((1 2 3) (2 4 6) (3 6 9))
           (-table (lambda (a b) (-sum (-zip-with '* a b))) '((1 2) (3 4)) '((1 3) (2 4)))
               ⇒ ((7 15) (10 22))
           (apply '-table 'list (-repeat 3 '(1 2)))
               ⇒ ((((1 1 1) (2 1 1)) ((1 2 1) (2 2 1))) (((1 1 2) (2 1 2)) ((1 2 2) (2 2 2))))
 
  -- Function: -table-flat (fn &rest lists)
      Compute flat outer product of LISTS using function FN.
 
      The function FN should have the same arity as the number of
      supplied lists.
 
      The outer product is computed by applying fn to all possible
      combinations created by taking one element from each list in order.
      The results are flattened, ignoring the tensor structure of the
      result.  This is equivalent to calling:
 
      (-flatten-n (1- (length lists)) (apply ’-table fn lists))
 
      but the implementation here is much more efficient.
 
      See also: ‘-flatten-n’ (*note -flatten-n::), ‘-table’ (*note
      -table::)
 
           (-table-flat 'list '(1 2 3) '(a b c))
               ⇒ ((1 a) (2 a) (3 a) (1 b) (2 b) (3 b) (1 c) (2 c) (3 c))
           (-table-flat '* '(1 2 3) '(1 2 3))
               ⇒ (1 2 3 2 4 6 3 6 9)
           (apply '-table-flat 'list (-repeat 3 '(1 2)))
               ⇒ ((1 1 1) (2 1 1) (1 2 1) (2 2 1) (1 1 2) (2 1 2) (1 2 2) (2 2 2))
 
  -- Function: -first (pred list)
      Return the first item in LIST for which PRED returns non-nil.
      Return nil if no such element is found.  To get the first item in
      the list no questions asked, use ‘car’.
 
      Alias: ‘-find’.
 
      This function’s anaphoric counterpart is ‘--first’.
 
           (-first #'natnump '(-1 0 1))
               ⇒ 0
           (-first #'null '(1 2 3))
               ⇒ nil
           (--first (> it 2) '(1 2 3))
               ⇒ 3
 
  -- Function: -last (pred list)
      Return the last x in LIST where (PRED x) is non-nil, else nil.
 
           (-last 'even? '(1 2 3 4 5 6 3 3 3))
               ⇒ 6
           (-last 'even? '(1 3 7 5 9))
               ⇒ nil
           (--last (> (length it) 3) '("a" "looong" "word" "and" "short" "one"))
               ⇒ "short"
 
  -- Function: -first-item (list)
      Return the first item of LIST, or nil on an empty list.
 
      See also: ‘-second-item’ (*note -second-item::), ‘-last-item’
      (*note -last-item::).
 
           (-first-item '(1 2 3))
               ⇒ 1
           (-first-item nil)
               ⇒ nil
           (let ((list (list 1 2 3))) (setf (-first-item list) 5) list)
               ⇒ (5 2 3)
 
  -- Function: -second-item (list)
      Return the second item of LIST, or nil if LIST is too short.
 
      See also: ‘-third-item’ (*note -third-item::).
 
           (-second-item '(1 2 3))
               ⇒ 2
           (-second-item nil)
               ⇒ nil
 
  -- Function: -third-item (list)
      Return the third item of LIST, or nil if LIST is too short.
 
      See also: ‘-fourth-item’ (*note -fourth-item::).
 
           (-third-item '(1 2 3))
               ⇒ 3
           (-third-item nil)
               ⇒ nil
 
  -- Function: -fourth-item (list)
      Return the fourth item of LIST, or nil if LIST is too short.
 
      See also: ‘-fifth-item’ (*note -fifth-item::).
 
           (-fourth-item '(1 2 3 4))
               ⇒ 4
           (-fourth-item nil)
               ⇒ nil
 
  -- Function: -fifth-item (list)
      Return the fifth item of LIST, or nil if LIST is too short.
 
      See also: ‘-last-item’ (*note -last-item::).
 
           (-fifth-item '(1 2 3 4 5))
               ⇒ 5
           (-fifth-item nil)
               ⇒ nil
 
  -- Function: -last-item (list)
      Return the last item of LIST, or nil on an empty list.
 
           (-last-item '(1 2 3))
               ⇒ 3
           (-last-item nil)
               ⇒ nil
           (let ((list (list 1 2 3))) (setf (-last-item list) 5) list)
               ⇒ (1 2 5)
 
  -- Function: -butlast (list)
      Return a list of all items in list except for the last.
 
           (-butlast '(1 2 3))
               ⇒ (1 2)
           (-butlast '(1 2))
               ⇒ (1)
           (-butlast '(1))
               ⇒ nil
 
  -- Function: -sort (comparator list)
      Sort LIST, stably, comparing elements using COMPARATOR.  Return the
      sorted list.  LIST is NOT modified by side effects.  COMPARATOR is
      called with two elements of LIST, and should return non-nil if the
      first element should sort before the second.
 
           (-sort '< '(3 1 2))
               ⇒ (1 2 3)
           (-sort '> '(3 1 2))
               ⇒ (3 2 1)
           (--sort (< it other) '(3 1 2))
               ⇒ (1 2 3)
 
  -- Function: -list (arg)
      Ensure ARG is a list.  If ARG is already a list, return it as is
      (not a copy).  Otherwise, return a new list with ARG as its only
      element.
 
      Another supported calling convention is (-list &rest ARGS).  In
      this case, if ARG is not a list, a new list with all of ARGS as
      elements is returned.  This use is supported for backward
      compatibility and is otherwise deprecated.
 
           (-list 1)
               ⇒ (1)
           (-list ())
               ⇒ ()
           (-list '(1 2 3))
               ⇒ (1 2 3)
 
  -- Function: -fix (fn list)
      Compute the (least) fixpoint of FN with initial input LIST.
 
      FN is called at least once, results are compared with ‘equal’.
 
           (-fix (lambda (l) (-non-nil (--mapcat (-split-at (/ (length it) 2) it) l))) '((1 2 3)))
               ⇒ ((1) (2) (3))
           (let ((l '((starwars scifi) (jedi starwars warrior)))) (--fix (-uniq (--mapcat (cons it (cdr (assq it l))) it)) '(jedi book)))
               ⇒ (jedi starwars warrior scifi book)
 
 
 File: dash.info,  Node: Tree operations,  Next: Threading macros,  Prev: Other list operations,  Up: Functions
 
 2.11 Tree operations
 ====================
 
 Functions pretending lists are trees.
 
  -- Function: -tree-seq (branch children tree)
      Return a sequence of the nodes in TREE, in depth-first search
      order.
 
      BRANCH is a predicate of one argument that returns non-nil if the
      passed argument is a branch, that is, a node that can have
      children.
 
      CHILDREN is a function of one argument that returns the children of
      the passed branch node.
 
      Non-branch nodes are simply copied.
 
           (-tree-seq 'listp 'identity '(1 (2 3) 4 (5 (6 7))))
               ⇒ ((1 (2 3) 4 (5 (6 7))) 1 (2 3) 2 3 4 (5 (6 7)) 5 (6 7) 6 7)
           (-tree-seq 'listp 'reverse '(1 (2 3) 4 (5 (6 7))))
               ⇒ ((1 (2 3) 4 (5 (6 7))) (5 (6 7)) (6 7) 7 6 5 4 (2 3) 3 2 1)
           (--tree-seq (vectorp it) (append it nil) [1 [2 3] 4 [5 [6 7]]])
               ⇒ ([1 [2 3] 4 [5 [6 7]]] 1 [2 3] 2 3 4 [5 [6 7]] 5 [6 7] 6 7)
 
  -- Function: -tree-map (fn tree)
      Apply FN to each element of TREE while preserving the tree
      structure.
 
           (-tree-map '1+ '(1 (2 3) (4 (5 6) 7)))
               ⇒ (2 (3 4) (5 (6 7) 8))
           (-tree-map '(lambda (x) (cons x (expt 2 x))) '(1 (2 3) 4))
               ⇒ ((1 . 2) ((2 . 4) (3 . 8)) (4 . 16))
           (--tree-map (length it) '("<body>" ("<p>" "text" "</p>") "</body>"))
               ⇒ (6 (3 4 4) 7)
 
  -- Function: -tree-map-nodes (pred fun tree)
      Call FUN on each node of TREE that satisfies PRED.
 
      If PRED returns nil, continue descending down this node.  If PRED
      returns non-nil, apply FUN to this node and do not descend further.
 
           (-tree-map-nodes 'vectorp (lambda (x) (-sum (append x nil))) '(1 [2 3] 4 (5 [6 7] 8)))
               ⇒ (1 5 4 (5 13 8))
           (-tree-map-nodes 'keywordp (lambda (x) (symbol-name x)) '(1 :foo 4 ((5 6 :bar) :baz 8)))
               ⇒ (1 ":foo" 4 ((5 6 ":bar") ":baz" 8))
           (--tree-map-nodes (eq (car-safe it) 'add-mode) (-concat it (list :mode 'emacs-lisp-mode)) '(with-mode emacs-lisp-mode (foo bar) (add-mode a b) (baz (add-mode c d))))
               ⇒ (with-mode emacs-lisp-mode (foo bar) (add-mode a b :mode emacs-lisp-mode) (baz (add-mode c d :mode emacs-lisp-mode)))
 
  -- Function: -tree-reduce (fn tree)
      Use FN to reduce elements of list TREE.  If elements of TREE are
      lists themselves, apply the reduction recursively.
 
      FN is first applied to first element of the list and second
      element, then on this result and third element from the list etc.
 
      See ‘-reduce-r’ (*note -reduce-r::) for how exactly are lists of
      zero or one element handled.
 
           (-tree-reduce '+ '(1 (2 3) (4 5)))
               ⇒ 15
           (-tree-reduce 'concat '("strings" (" on" " various") ((" levels"))))
               ⇒ "strings on various levels"
           (--tree-reduce (cond ((stringp it) (concat it " " acc)) (t (let ((sn (symbol-name it))) (concat "<" sn ">" acc "</" sn ">")))) '(body (p "some words") (div "more" (b "bold") "words")))
               ⇒ "<body><p>some words</p> <div>more <b>bold</b> words</div></body>"
 
  -- Function: -tree-reduce-from (fn init-value tree)
      Use FN to reduce elements of list TREE.  If elements of TREE are
      lists themselves, apply the reduction recursively.
 
      FN is first applied to INIT-VALUE and first element of the list,
      then on this result and second element from the list etc.
 
      The initial value is ignored on cons pairs as they always contain
      two elements.
 
           (-tree-reduce-from '+ 1 '(1 (1 1) ((1))))
               ⇒ 8
           (--tree-reduce-from (-concat acc (list it)) nil '(1 (2 3 (4 5)) (6 7)))
               ⇒ ((7 6) ((5 4) 3 2) 1)
 
  -- Function: -tree-mapreduce (fn folder tree)
      Apply FN to each element of TREE, and make a list of the results.
      If elements of TREE are lists themselves, apply FN recursively to
      elements of these nested lists.
 
      Then reduce the resulting lists using FOLDER and initial value
      INIT-VALUE.  See ‘-reduce-r-from’ (*note -reduce-r-from::).
 
      This is the same as calling ‘-tree-reduce’ (*note -tree-reduce::)
      after ‘-tree-map’ (*note -tree-map::) but is twice as fast as it
      only traverse the structure once.
 
           (-tree-mapreduce 'list 'append '(1 (2 (3 4) (5 6)) (7 (8 9))))
               ⇒ (1 2 3 4 5 6 7 8 9)
           (--tree-mapreduce 1 (+ it acc) '(1 (2 (4 9) (2 1)) (7 (4 3))))
               ⇒ 9
           (--tree-mapreduce 0 (max acc (1+ it)) '(1 (2 (4 9) (2 1)) (7 (4 3))))
               ⇒ 3
 
  -- Function: -tree-mapreduce-from (fn folder init-value tree)
      Apply FN to each element of TREE, and make a list of the results.
      If elements of TREE are lists themselves, apply FN recursively to
      elements of these nested lists.
 
      Then reduce the resulting lists using FOLDER and initial value
      INIT-VALUE.  See ‘-reduce-r-from’ (*note -reduce-r-from::).
 
      This is the same as calling ‘-tree-reduce-from’ (*note
      -tree-reduce-from::) after ‘-tree-map’ (*note -tree-map::) but is
      twice as fast as it only traverse the structure once.
 
           (-tree-mapreduce-from 'identity '* 1 '(1 (2 (3 4) (5 6)) (7 (8 9))))
               ⇒ 362880
           (--tree-mapreduce-from (+ it it) (cons it acc) nil '(1 (2 (4 9) (2 1)) (7 (4 3))))
               ⇒ (2 (4 (8 18) (4 2)) (14 (8 6)))
           (concat "{" (--tree-mapreduce-from (cond ((-cons-pair? it) (concat (symbol-name (car it)) " -> " (symbol-name (cdr it)))) (t (concat (symbol-name it) " : {"))) (concat it (unless (or (equal acc "}") (equal (substring it (1- (length it))) "{")) ", ") acc) "}" '((elisp-mode (foo (bar . booze)) (baz . qux)) (c-mode (foo . bla) (bum . bam)))))
               ⇒ "{elisp-mode : {foo : {bar -> booze}, baz -> qux}, c-mode : {foo -> bla, bum -> bam}}"
 
  -- Function: -clone (list)
      Create a deep copy of LIST.  The new list has the same elements and
      structure but all cons are replaced with new ones.  This is useful
      when you need to clone a structure such as plist or alist.
 
           (let* ((a '(1 2 3)) (b (-clone a))) (nreverse a) b)
               ⇒ (1 2 3)
 
 
 File: dash.info,  Node: Threading macros,  Next: Binding,  Prev: Tree operations,  Up: Functions
 
 2.12 Threading macros
 =====================
 
 Macros that conditionally combine sequential forms for brevity or
 readability.
 
  -- Macro: -> (x &optional form &rest more)
      Thread the expr through the forms.  Insert X as the second item in
      the first form, making a list of it if it is not a list already.
      If there are more forms, insert the first form as the second item
      in second form, etc.
 
           (-> '(2 3 5))
               ⇒ (2 3 5)
           (-> '(2 3 5) (append '(8 13)))
               ⇒ (2 3 5 8 13)
           (-> '(2 3 5) (append '(8 13)) (-slice 1 -1))
               ⇒ (3 5 8)
 
  -- Macro: ->> (x &optional form &rest more)
      Thread the expr through the forms.  Insert X as the last item in
      the first form, making a list of it if it is not a list already.
      If there are more forms, insert the first form as the last item in
      second form, etc.
 
           (->> '(1 2 3) (-map 'square))
               ⇒ (1 4 9)
           (->> '(1 2 3) (-map 'square) (-remove 'even?))
               ⇒ (1 9)
           (->> '(1 2 3) (-map 'square) (-reduce '+))
               ⇒ 14
 
  -- Macro: --> (x &rest forms)
      Starting with the value of X, thread each expression through FORMS.
 
      Insert X at the position signified by the symbol ‘it’ in the first
      form.  If there are more forms, insert the first form at the
      position signified by ‘it’ in in second form, etc.
 
           (--> "def" (concat "abc" it "ghi"))
               ⇒ "abcdefghi"
           (--> "def" (concat "abc" it "ghi") (upcase it))
               ⇒ "ABCDEFGHI"
           (--> "def" (concat "abc" it "ghi") upcase)
               ⇒ "ABCDEFGHI"
 
  -- Macro: -as-> (value variable &rest forms)
      Starting with VALUE, thread VARIABLE through FORMS.
 
      In the first form, bind VARIABLE to VALUE.  In the second form,
      bind VARIABLE to the result of the first form, and so forth.
 
           (-as-> 3 my-var (1+ my-var) (list my-var) (mapcar (lambda (ele) (* 2 ele)) my-var))
               ⇒ (8)
           (-as-> 3 my-var 1+)
               ⇒ 4
           (-as-> 3 my-var)
               ⇒ 3
 
  -- Macro: -some-> (x &optional form &rest more)
      When expr is non-nil, thread it through the first form (via ‘->’
      (*note ->::)), and when that result is non-nil, through the next
      form, etc.
 
           (-some-> '(2 3 5))
               ⇒ (2 3 5)
           (-some-> 5 square)
               ⇒ 25
           (-some-> 5 even? square)
               ⇒ nil
 
  -- Macro: -some->> (x &optional form &rest more)
      When expr is non-nil, thread it through the first form (via ‘->>’
      (*note ->>::)), and when that result is non-nil, through the next
      form, etc.
 
           (-some->> '(1 2 3) (-map 'square))
               ⇒ (1 4 9)
           (-some->> '(1 3 5) (-last 'even?) (+ 100))
               ⇒ nil
           (-some->> '(2 4 6) (-last 'even?) (+ 100))
               ⇒ 106
 
  -- Macro: -some--> (expr &rest forms)
      Thread EXPR through FORMS via ‘-->’ (*note -->::), while the result
      is non-nil.  When EXPR evaluates to non-nil, thread the result
      through the first of FORMS, and when that result is non-nil, thread
      it through the next form, etc.
 
           (-some--> "def" (concat "abc" it "ghi"))
               ⇒ "abcdefghi"
           (-some--> nil (concat "abc" it "ghi"))
               ⇒ nil
           (-some--> '(0 1) (-remove #'natnump it) (append it it) (-map #'1+ it))
               ⇒ ()
 
  -- Macro: -doto (init &rest forms)
      Evaluate INIT and pass it as argument to FORMS with ‘->’ (*note
      ->::).  The RESULT of evaluating INIT is threaded through each of
      FORMS individually using ‘->’ (*note ->::), which see.  The return
      value is RESULT, which FORMS may have modified by side effect.
 
           (-doto (list 1 2 3) pop pop)
               ⇒ (3)
           (-doto (cons 1 2) (setcar 3) (setcdr 4))
               ⇒ (3 . 4)
           (gethash 'k (--doto (make-hash-table) (puthash 'k 'v it)))
               ⇒ v
 
 
 File: dash.info,  Node: Binding,  Next: Side effects,  Prev: Threading macros,  Up: Functions
 
 2.13 Binding
 ============
 
 Macros that combine ‘let’ and ‘let*’ with destructuring and flow
 control.
 
  -- Macro: -when-let ((var val) &rest body)
      If VAL evaluates to non-nil, bind it to VAR and execute body.
 
      Note: binding is done according to ‘-let’ (*note -let::).
 
           (-when-let (match-index (string-match "d" "abcd")) (+ match-index 2))
               ⇒ 5
           (-when-let ((&plist :foo foo) (list :foo "foo")) foo)
               ⇒ "foo"
           (-when-let ((&plist :foo foo) (list :bar "bar")) foo)
               ⇒ nil
 
  -- Macro: -when-let* (vars-vals &rest body)
      If all VALS evaluate to true, bind them to their corresponding VARS
      and execute body.  VARS-VALS should be a list of (VAR VAL) pairs.
 
      Note: binding is done according to ‘-let*’ (*note -let*::).  VALS
      are evaluated sequentially, and evaluation stops after the first
      nil VAL is encountered.
 
           (-when-let* ((x 5) (y 3) (z (+ y 4))) (+ x y z))
               ⇒ 15
           (-when-let* ((x 5) (y nil) (z 7)) (+ x y z))
               ⇒ nil
 
  -- Macro: -if-let ((var val) then &rest else)
      If VAL evaluates to non-nil, bind it to VAR and do THEN, otherwise
      do ELSE.
 
      Note: binding is done according to ‘-let’ (*note -let::).
 
           (-if-let (match-index (string-match "d" "abc")) (+ match-index 3) 7)
               ⇒ 7
           (--if-let (even? 4) it nil)
               ⇒ t
 
  -- Macro: -if-let* (vars-vals then &rest else)
      If all VALS evaluate to true, bind them to their corresponding VARS
      and do THEN, otherwise do ELSE.  VARS-VALS should be a list of (VAR
      VAL) pairs.
 
      Note: binding is done according to ‘-let*’ (*note -let*::).  VALS
      are evaluated sequentially, and evaluation stops after the first
      nil VAL is encountered.
 
           (-if-let* ((x 5) (y 3) (z 7)) (+ x y z) "foo")
               ⇒ 15
           (-if-let* ((x 5) (y nil) (z 7)) (+ x y z) "foo")
               ⇒ "foo"
           (-if-let* (((_ _ x) '(nil nil 7))) x)
               ⇒ 7
 
  -- Macro: -let (varlist &rest body)
      Bind variables according to VARLIST then eval BODY.
 
      VARLIST is a list of lists of the form (PATTERN SOURCE).  Each
      PATTERN is matched against the SOURCE "structurally".  SOURCE is
      only evaluated once for each PATTERN.  Each PATTERN is matched
      recursively, and can therefore contain sub-patterns which are
      matched against corresponding sub-expressions of SOURCE.
 
      All the SOURCEs are evalled before any symbols are bound (i.e.  "in
      parallel").
 
      If VARLIST only contains one (PATTERN SOURCE) element, you can
      optionally specify it using a vector and discarding the outer-most
      parens.  Thus
 
      (-let ((PATTERN SOURCE)) ...)
 
      becomes
 
      (-let [PATTERN SOURCE] ...).
 
      ‘-let’ (*note -let::) uses a convention of not binding places
      (symbols) starting with _ whenever it’s possible.  You can use this
      to skip over entries you don’t care about.  However, this is not
      *always* possible (as a result of implementation) and these symbols
      might get bound to undefined values.
 
      Following is the overview of supported patterns.  Remember that
      patterns can be matched recursively, so every a, b, aK in the
      following can be a matching construct and not necessarily a
      symbol/variable.
 
      Symbol:
 
      a - bind the SOURCE to A.  This is just like regular ‘let’.
 
      Conses and lists:
 
      (a) - bind ‘car’ of cons/list to A
 
      (a .  b) - bind car of cons to A and ‘cdr’ to B
 
      (a b) - bind car of list to A and ‘cadr’ to B
 
      (a1 a2 a3 ...) - bind 0th car of list to A1, 1st to A2, 2nd to
      A3...
 
      (a1 a2 a3 ... aN .  rest) - as above, but bind the Nth cdr to REST.
 
      Vectors:
 
      [a] - bind 0th element of a non-list sequence to A (works with
      vectors, strings, bit arrays...)
 
      [a1 a2 a3 ...] - bind 0th element of non-list sequence to A0, 1st
      to A1, 2nd to A2, ...  If the PATTERN is shorter than SOURCE, the
      values at places not in PATTERN are ignored.  If the PATTERN is
      longer than SOURCE, an ‘error’ is thrown.
 
      [a1 a2 a3 ... &rest rest] - as above, but bind the rest of the
      sequence to REST.  This is conceptually the same as improper list
      matching (a1 a2 ... aN .  rest)
 
      Key/value stores:
 
      (&plist key0 a0 ... keyN aN) - bind value mapped by keyK in the
      SOURCE plist to aK. If the value is not found, aK is nil.  Uses
      ‘plist-get’ to fetch values.
 
      (&alist key0 a0 ... keyN aN) - bind value mapped by keyK in the
      SOURCE alist to aK. If the value is not found, aK is nil.  Uses
      ‘assoc’ to fetch values.
 
      (&hash key0 a0 ... keyN aN) - bind value mapped by keyK in the
      SOURCE hash table to aK. If the value is not found, aK is nil.
      Uses ‘gethash’ to fetch values.
 
      Further, special keyword &keys supports "inline" matching of
      plist-like key-value pairs, similarly to &keys keyword of
      ‘cl-defun’.
 
      (a1 a2 ... aN &keys key1 b1 ... keyN bK)
 
      This binds N values from the list to a1 ... aN, then interprets the
      cdr as a plist (see key/value matching above).
 
      A shorthand notation for kv-destructuring exists which allows the
      patterns be optionally left out and derived from the key name in
      the following fashion:
 
      - a key :foo is converted into ‘foo’ pattern, - a key ’bar is
      converted into ‘bar’ pattern, - a key "baz" is converted into ‘baz’
      pattern.
 
      That is, the entire value under the key is bound to the derived
      variable without any further destructuring.
 
      This is possible only when the form following the key is not a
      valid pattern (i.e.  not a symbol, a cons cell or a vector).
      Otherwise the matching proceeds as usual and in case of an invalid
      spec fails with an error.
 
      Thus the patterns are normalized as follows:
 
      ;; derive all the missing patterns (&plist :foo ’bar "baz") =>
      (&plist :foo foo ’bar bar "baz" baz)
 
      ;; we can specify some but not others (&plist :foo ’bar
      explicit-bar) => (&plist :foo foo ’bar explicit-bar)
 
      ;; nothing happens, we store :foo in x (&plist :foo x) => (&plist
      :foo x)
 
      ;; nothing happens, we match recursively (&plist :foo (a b c)) =>
      (&plist :foo (a b c))
 
      You can name the source using the syntax SYMBOL &as PATTERN.  This
      syntax works with lists (proper or improper), vectors and all types
      of maps.
 
      (list &as a b c) (list 1 2 3)
 
      binds A to 1, B to 2, C to 3 and LIST to (1 2 3).
 
      Similarly:
 
      (bounds &as beg .  end) (cons 1 2)
 
      binds BEG to 1, END to 2 and BOUNDS to (1 .  2).
 
      (items &as first .  rest) (list 1 2 3)
 
      binds FIRST to 1, REST to (2 3) and ITEMS to (1 2 3)
 
      [vect &as _ b c] [1 2 3]
 
      binds B to 2, C to 3 and VECT to [1 2 3] (_ avoids binding as
      usual).
 
      (plist &as &plist :b b) (list :a 1 :b 2 :c 3)
 
      binds B to 2 and PLIST to (:a 1 :b 2 :c 3).  Same for &alist and
      &hash.
 
      This is especially useful when we want to capture the result of a
      computation and destructure at the same time.  Consider the form
      (function-returning-complex-structure) returning a list of two
      vectors with two items each.  We want to capture this entire result
      and pass it to another computation, but at the same time we want to
      get the second item from each vector.  We can achieve it with
      pattern
 
      (result &as [_ a] [_ b]) (function-returning-complex-structure)
 
      Note: Clojure programmers may know this feature as the ":as
      binding".  The difference is that we put the &as at the front
      because we need to support improper list binding.
 
           (-let (([a (b c) d] [1 (2 3) 4])) (list a b c d))
               ⇒ (1 2 3 4)
           (-let [(a b c . d) (list 1 2 3 4 5 6)] (list a b c d))
               ⇒ (1 2 3 (4 5 6))
           (-let [(&plist :foo foo :bar bar) (list :baz 3 :foo 1 :qux 4 :bar 2)] (list foo bar))
               ⇒ (1 2)
 
  -- Macro: -let* (varlist &rest body)
      Bind variables according to VARLIST then eval BODY.
 
      VARLIST is a list of lists of the form (PATTERN SOURCE).  Each
      PATTERN is matched against the SOURCE structurally.  SOURCE is only
      evaluated once for each PATTERN.
 
      Each SOURCE can refer to the symbols already bound by this VARLIST.
      This is useful if you want to destructure SOURCE recursively but
      also want to name the intermediate structures.
 
      See ‘-let’ (*note -let::) for the list of all possible patterns.
 
           (-let* (((a . b) (cons 1 2)) ((c . d) (cons 3 4))) (list a b c d))
               ⇒ (1 2 3 4)
           (-let* (((a . b) (cons 1 (cons 2 3))) ((c . d) b)) (list a b c d))
               ⇒ (1 (2 . 3) 2 3)
           (-let* (((&alist "foo" foo "bar" bar) (list (cons "foo" 1) (cons "bar" (list 'a 'b 'c)))) ((a b c) bar)) (list foo a b c bar))
               ⇒ (1 a b c (a b c))
 
  -- Macro: -lambda (match-form &rest body)
      Return a lambda which destructures its input as MATCH-FORM and
      executes BODY.
 
      Note that you have to enclose the MATCH-FORM in a pair of parens,
      such that:
 
      (-lambda (x) body) (-lambda (x y ...) body)
 
      has the usual semantics of ‘lambda’.  Furthermore, these get
      translated into normal ‘lambda’, so there is no performance
      penalty.
 
      See ‘-let’ (*note -let::) for a description of the destructuring
      mechanism.
 
           (-map (-lambda ((x y)) (+ x y)) '((1 2) (3 4) (5 6)))
               ⇒ (3 7 11)
           (-map (-lambda ([x y]) (+ x y)) '([1 2] [3 4] [5 6]))
               ⇒ (3 7 11)
           (funcall (-lambda ((_ . a) (_ . b)) (-concat a b)) '(1 2 3) '(4 5 6))
               ⇒ (2 3 5 6)
 
  -- Macro: -setq ([match-form val] ...)
      Bind each MATCH-FORM to the value of its VAL.
 
      MATCH-FORM destructuring is done according to the rules of ‘-let’
      (*note -let::).
 
      This macro allows you to bind multiple variables by destructuring
      the value, so for example:
 
      (-setq (a b) x (&plist :c c) plist)
 
      expands roughly speaking to the following code
 
      (setq a (car x) b (cadr x) c (plist-get plist :c))
 
      Care is taken to only evaluate each VAL once so that in case of
      multiple assignments it does not cause unexpected side effects.
 
           (let (a) (-setq a 1) a)
               ⇒ 1
           (let (a b) (-setq (a b) (list 1 2)) (list a b))
               ⇒ (1 2)
           (let (c) (-setq (&plist :c c) (list :c "c")) c)
               ⇒ "c"
 
 
 File: dash.info,  Node: Side effects,  Next: Destructive operations,  Prev: Binding,  Up: Functions
 
 2.14 Side effects
 =================
 
 Functions iterating over lists for side effect only.
 
  -- Function: -each (list fn)
      Call FN on each element of LIST.  Return nil; this function is
      intended for side effects.
 
      Its anaphoric counterpart is ‘--each’.
 
      For access to the current element’s index in LIST, see
      ‘-each-indexed’ (*note -each-indexed::).
 
           (let (l) (-each '(1 2 3) (lambda (x) (push x l))) l)
               ⇒ (3 2 1)
           (let (l) (--each '(1 2 3) (push it l)) l)
               ⇒ (3 2 1)
           (-each '(1 2 3) #'identity)
               ⇒ nil
 
  -- Function: -each-while (list pred fn)
      Call FN on each ITEM in LIST, while (PRED ITEM) is non-nil.  Once
      an ITEM is reached for which PRED returns nil, FN is no longer
      called.  Return nil; this function is intended for side effects.
 
      Its anaphoric counterpart is ‘--each-while’.
 
           (let (l) (-each-while '(2 4 5 6) #'even? (lambda (x) (push x l))) l)
               ⇒ (4 2)
           (let (l) (--each-while '(1 2 3 4) (< it 3) (push it l)) l)
               ⇒ (2 1)
           (let ((s 0)) (--each-while '(1 3 4 5) (< it 5) (setq s (+ s it))) s)
               ⇒ 8
 
  -- Function: -each-indexed (list fn)
      Call FN on each index and element of LIST.  For each ITEM at INDEX
      in LIST, call (funcall FN INDEX ITEM).  Return nil; this function
      is intended for side effects.
 
      See also: ‘-map-indexed’ (*note -map-indexed::).
 
           (let (l) (-each-indexed '(a b c) (lambda (i x) (push (list x i) l))) l)
               ⇒ ((c 2) (b 1) (a 0))
           (let (l) (--each-indexed '(a b c) (push (list it it-index) l)) l)
               ⇒ ((c 2) (b 1) (a 0))
           (let (l) (--each-indexed () (push it l)) l)
               ⇒ ()
 
  -- Function: -each-r (list fn)
      Call FN on each element of LIST in reversed order.  Return nil;
      this function is intended for side effects.
 
      Its anaphoric counterpart is ‘--each-r’.
 
           (let (l) (-each-r '(1 2 3) (lambda (x) (push x l))) l)
               ⇒ (1 2 3)
           (let (l) (--each-r '(1 2 3) (push it l)) l)
               ⇒ (1 2 3)
           (-each-r '(1 2 3) #'identity)
               ⇒ nil
 
  -- Function: -each-r-while (list pred fn)
      Call FN on each ITEM in reversed LIST, while (PRED ITEM) is
      non-nil.  Once an ITEM is reached for which PRED returns nil, FN is
      no longer called.  Return nil; this function is intended for side
      effects.
 
      Its anaphoric counterpart is ‘--each-r-while’.
 
           (let (l) (-each-r-while '(2 4 5 6) #'even? (lambda (x) (push x l))) l)
               ⇒ (6)
           (let (l) (--each-r-while '(1 2 3 4) (>= it 3) (push it l)) l)
               ⇒ (3 4)
           (let ((s 0)) (--each-r-while '(1 2 3 5) (> it 1) (setq s (+ s it))) s)
               ⇒ 10
 
  -- Function: -dotimes (num fn)
      Call FN NUM times, presumably for side effects.  FN is called with
      a single argument on successive integers running from 0, inclusive,
      to NUM, exclusive.  FN is not called if NUM is less than 1.
 
      This function’s anaphoric counterpart is ‘--dotimes’.
 
           (let (s) (-dotimes 3 (lambda (n) (push n s))) s)
               ⇒ (2 1 0)
           (let (s) (-dotimes 0 (lambda (n) (push n s))) s)
               ⇒ ()
           (let (s) (--dotimes 5 (push it s)) s)
               ⇒ (4 3 2 1 0)
 
 
 File: dash.info,  Node: Destructive operations,  Next: Function combinators,  Prev: Side effects,  Up: Functions
 
 2.15 Destructive operations
 ===========================
 
 Macros that modify variables holding lists.
 
  -- Macro: !cons (car cdr)
      Destructive: Set CDR to the cons of CAR and CDR.
 
           (let (l) (!cons 5 l) l)
               ⇒ (5)
           (let ((l '(3))) (!cons 5 l) l)
               ⇒ (5 3)
 
  -- Macro: !cdr (list)
      Destructive: Set LIST to the cdr of LIST.
 
           (let ((l '(3))) (!cdr l) l)
               ⇒ ()
           (let ((l '(3 5))) (!cdr l) l)
               ⇒ (5)
 
 
 File: dash.info,  Node: Function combinators,  Prev: Destructive operations,  Up: Functions
 
 2.16 Function combinators
 =========================
 
 Functions that manipulate and compose other functions.
 
  -- Function: -partial (fun &rest args)
      Return a function that is a partial application of FUN to ARGS.
      ARGS is a list of the first N arguments to pass to FUN.  The result
      is a new function which does the same as FUN, except that the first
      N arguments are fixed at the values with which this function was
      called.
 
           (funcall (-partial #'+ 5))
               ⇒ 5
           (funcall (-partial #'- 5) 3)
               ⇒ 2
           (funcall (-partial #'+ 5 2) 3)
               ⇒ 10
 
  -- Function: -rpartial (fn &rest args)
      Return a function that is a partial application of FN to ARGS.
      ARGS is a list of the last N arguments to pass to FN.  The result
      is a new function which does the same as FN, except that the last N
      arguments are fixed at the values with which this function was
      called.  This is like ‘-partial’ (*note -partial::), except the
      arguments are fixed starting from the right rather than the left.
 
           (funcall (-rpartial #'- 5))
               ⇒ -5
           (funcall (-rpartial #'- 5) 8)
               ⇒ 3
           (funcall (-rpartial #'- 5 2) 10)
               ⇒ 3
 
  -- Function: -juxt (&rest fns)
      Return a function that is the juxtaposition of FNS.  The returned
      function takes a variable number of ARGS, applies each of FNS in
      turn to ARGS, and returns the list of results.
 
           (funcall (-juxt) 1 2)
               ⇒ ()
           (funcall (-juxt #'+ #'- #'* #'/) 7 5)
               ⇒ (12 2 35 1)
           (mapcar (-juxt #'number-to-string #'1+) '(1 2))
               ⇒ (("1" 2) ("2" 3))
 
  -- Function: -compose (&rest fns)
      Compose FNS into a single composite function.  Return a function
      that takes a variable number of ARGS, applies the last function in
      FNS to ARGS, and returns the result of calling each remaining
      function on the result of the previous function, right-to-left.  If
      no FNS are given, return a variadic ‘identity’ function.
 
           (funcall (-compose #'- #'1+ #'+) 1 2 3)
               ⇒ -7
           (funcall (-compose #'identity #'1+) 3)
               ⇒ 4
           (mapcar (-compose #'not #'stringp) '(nil ""))
               ⇒ (t nil)
 
  -- Function: -applify (fn)
      Return a function that applies FN to a single list of args.  This
      changes the arity of FN from taking N distinct arguments to taking
      1 argument which is a list of N arguments.
 
           (funcall (-applify #'+) nil)
               ⇒ 0
           (mapcar (-applify #'+) '((1 1 1) (1 2 3) (5 5 5)))
               ⇒ (3 6 15)
           (funcall (-applify #'<) '(3 6))
               ⇒ t
 
  -- Function: -on (op trans)
      Return a function that calls TRANS on each arg and OP on the
      results.  The returned function takes a variable number of
      arguments, calls the function TRANS on each one in turn, and then
      passes those results as the list of arguments to OP, in the same
      order.
 
      For example, the following pairs of expressions are morally
      equivalent:
 
      (funcall (-on #’+ #’1+) 1 2 3) = (+ (1+ 1) (1+ 2) (1+ 3)) (funcall
      (-on #’+ #’1+)) = (+)
 
           (-sort (-on #'< #'length) '((1 2 3) (1) (1 2)))
               ⇒ ((1) (1 2) (1 2 3))
           (funcall (-on #'min #'string-to-number) "22" "2" "1" "12")
               ⇒ 1
           (-min-by (-on #'> #'length) '((1 2 3) (4) (1 2)))
               ⇒ (4)
 
  -- Function: -flip (fn)
      Return a function that calls FN with its arguments reversed.  The
      returned function takes the same number of arguments as FN.
 
      For example, the following two expressions are morally equivalent:
 
      (funcall (-flip #’-) 1 2) = (- 2 1)
 
      See also: ‘-rotate-args’ (*note -rotate-args::).
 
           (-sort (-flip #'<) '(4 3 6 1))
               ⇒ (6 4 3 1)
           (funcall (-flip #'-) 3 2 1 10)
               ⇒ 4
           (funcall (-flip #'1+) 1)
               ⇒ 2
 
  -- Function: -rotate-args (n fn)
      Return a function that calls FN with args rotated N places to the
      right.  The returned function takes the same number of arguments as
      FN, rotates the list of arguments N places to the right (left if N
      is negative) just like ‘-rotate’ (*note -rotate::), and applies FN
      to the result.
 
      See also: ‘-flip’ (*note -flip::).
 
           (funcall (-rotate-args -1 #'list) 1 2 3 4)
               ⇒ (2 3 4 1)
           (funcall (-rotate-args 1 #'-) 1 10 100)
               ⇒ 89
           (funcall (-rotate-args 2 #'list) 3 4 5 1 2)
               ⇒ (1 2 3 4 5)
 
  -- Function: -const (c)
      Return a function that returns C ignoring any additional arguments.
 
      In types: a -> b -> a
 
           (funcall (-const 2) 1 3 "foo")
               ⇒ 2
           (mapcar (-const 1) '("a" "b" "c" "d"))
               ⇒ (1 1 1 1)
           (-sum (mapcar (-const 1) '("a" "b" "c" "d")))
               ⇒ 4
 
  -- Macro: -cut (&rest params)
      Take n-ary function and n arguments and specialize some of them.
      Arguments denoted by <> will be left unspecialized.
 
      See SRFI-26 for detailed description.
 
           (funcall (-cut list 1 <> 3 <> 5) 2 4)
               ⇒ (1 2 3 4 5)
           (-map (-cut funcall <> 5) `(1+ 1- ,(lambda (x) (/ 1.0 x))))
               ⇒ (6 4 0.2)
           (-map (-cut <> 1 2 3) '(list vector string))
               ⇒ ((1 2 3) [1 2 3] "\1\2\3")
 
  -- Function: -not (pred)
      Return a predicate that negates the result of PRED.  The returned
      predicate passes its arguments to PRED.  If PRED returns nil, the
      result is non-nil; otherwise the result is nil.
 
      See also: ‘-andfn’ (*note -andfn::) and ‘-orfn’ (*note -orfn::).
 
           (funcall (-not #'numberp) "5")
               ⇒ t
           (-sort (-not #'<) '(5 2 1 0 6))
               ⇒ (6 5 2 1 0)
           (-filter (-not (-partial #'< 4)) '(1 2 3 4 5 6 7 8))
               ⇒ (1 2 3 4)
 
  -- Function: -orfn (&rest preds)
      Return a predicate that returns the first non-nil result of PREDS.
      The returned predicate takes a variable number of arguments, passes
      them to each predicate in PREDS in turn until one of them returns
      non-nil, and returns that non-nil result without calling the
      remaining PREDS.  If all PREDS return nil, or if no PREDS are
      given, the returned predicate returns nil.
 
      See also: ‘-andfn’ (*note -andfn::) and ‘-not’ (*note -not::).
 
           (-filter (-orfn #'natnump #'booleanp) '(1 nil "a" -4 b c t))
               ⇒ (1 nil t)
           (funcall (-orfn #'symbolp (-cut string-match-p "x" <>)) "axe")
               ⇒ 1
           (funcall (-orfn #'= #'+) 1 1)
               ⇒ t
 
  -- Function: -andfn (&rest preds)
      Return a predicate that returns non-nil if all PREDS do so.  The
      returned predicate P takes a variable number of arguments and
      passes them to each predicate in PREDS in turn.  If any one of
      PREDS returns nil, P also returns nil without calling the remaining
      PREDS.  If all PREDS return non-nil, P returns the last such value.
      If no PREDS are given, P always returns non-nil.
 
      See also: ‘-orfn’ (*note -orfn::) and ‘-not’ (*note -not::).
 
           (-filter (-andfn #'numberp (-cut < <> 5)) '(a 1 b 6 c 2))
               ⇒ (1 2)
           (mapcar (-andfn #'numberp #'1+) '(a 1 b 6))
               ⇒ (nil 2 nil 7)
           (funcall (-andfn #'= #'+) 1 1)
               ⇒ 2
 
  -- Function: -iteratefn (fn n)
      Return a function FN composed N times with itself.
 
      FN is a unary function.  If you need to use a function of higher
      arity, use ‘-applify’ (*note -applify::) first to turn it into a
      unary function.
 
      With n = 0, this acts as identity function.
 
      In types: (a -> a) -> Int -> a -> a.
 
      This function satisfies the following law:
 
      (funcall (-iteratefn fn n) init) = (-last-item (-iterate fn init
      (1+ n))).
 
           (funcall (-iteratefn (lambda (x) (* x x)) 3) 2)
               ⇒ 256
           (funcall (-iteratefn '1+ 3) 1)
               ⇒ 4
           (funcall (-iteratefn 'cdr 3) '(1 2 3 4 5))
               ⇒ (4 5)
 
  -- Function: -fixfn (fn &optional equal-test halt-test)
      Return a function that computes the (least) fixpoint of FN.
 
      FN must be a unary function.  The returned lambda takes a single
      argument, X, the initial value for the fixpoint iteration.  The
      iteration halts when either of the following conditions is
      satisfied:
 
      1.  Iteration converges to the fixpoint, with equality being tested
      using EQUAL-TEST.  If EQUAL-TEST is not specified, ‘equal’ is used.
      For functions over the floating point numbers, it may be necessary
      to provide an appropriate approximate comparison test.
 
      2.  HALT-TEST returns a non-nil value.  HALT-TEST defaults to a
      simple counter that returns t after ‘-fixfn-max-iterations’, to
      guard against infinite iteration.  Otherwise, HALT-TEST must be a
      function that accepts a single argument, the current value of X,
      and returns non-nil as long as iteration should continue.  In this
      way, a more sophisticated convergence test may be supplied by the
      caller.
 
      The return value of the lambda is either the fixpoint or, if
      iteration halted before converging, a cons with car ‘halted’ and
      cdr the final output from HALT-TEST.
 
      In types: (a -> a) -> a -> a.
 
           (funcall (-fixfn #'cos #'approx=) 0.7)
               ⇒ 0.7390851332151607
           (funcall (-fixfn (lambda (x) (expt (+ x 10) 0.25))) 2.0)
               ⇒ 1.8555845286409378
           (funcall (-fixfn #'sin #'approx=) 0.1)
               ⇒ (halted . t)
 
  -- Function: -prodfn (&rest fns)
      Take a list of n functions and return a function that takes a list
      of length n, applying i-th function to i-th element of the input
      list.  Returns a list of length n.
 
      In types (for n=2): ((a -> b), (c -> d)) -> (a, c) -> (b, d)
 
      This function satisfies the following laws:
 
      (-compose (-prodfn f g ...) (-prodfn f’ g’ ...)) = (-prodfn
      (-compose f f’) (-compose g g’) ...) (-prodfn f g ...) = (-juxt
      (-compose f (-partial ’nth 0)) (-compose g (-partial ’nth 1)) ...)
      (-compose (-prodfn f g ...) (-juxt f’ g’ ...)) = (-juxt (-compose f
      f’) (-compose g g’) ...) (-compose (-partial ’nth n) (-prod f1 f2
      ...)) = (-compose fn (-partial ’nth n))
 
           (funcall (-prodfn '1+ '1- 'number-to-string) '(1 2 3))
               ⇒ (2 1 "3")
           (-map (-prodfn '1+ '1-) '((1 2) (3 4) (5 6) (7 8)))
               ⇒ ((2 1) (4 3) (6 5) (8 7))
           (apply '+ (funcall (-prodfn 'length 'string-to-number) '((1 2 3) "15")))
               ⇒ 18
 
 
 File: dash.info,  Node: Development,  Next: FDL,  Prev: Functions,  Up: Top
 
 3 Development
 *************
 
 The Dash repository is hosted on GitHub at
 <https://github.com/magnars/dash.el>.
 
 * Menu:
 
 * Contribute::          How to contribute.
 * Contributors::        List of contributors.
 
 
 File: dash.info,  Node: Contribute,  Next: Contributors,  Up: Development
 
 3.1 Contribute
 ==============
 
 Yes, please do.  Pure functions in the list manipulation realm only,
 please.  There’s a suite of examples/tests in ‘dev/examples.el’, so
 remember to add tests for your additions, or they may get broken later.
 
    Run the tests with ‘make check’.  Regenerate the docs with ‘make
 docs’.  Contributors are encouraged to install these commands as a Git
 pre-commit hook, so that the tests are always running and the docs are
 always in sync:
 
      $ cp dev/pre-commit.sh .git/hooks/pre-commit
 
    Oh, and don’t edit ‘README.md’ or ‘dash.texi’ directly, as they are
 auto-generated.  Instead, change their respective templates
 ‘readme-template.md’ or ‘dash-template.texi’.
 
    To ensure that Dash can be distributed with GNU ELPA or Emacs, we
 require that all contributors assign copyright to the Free Software
 Foundation.  For more on this, *note (emacs)Copyright Assignment::.
 
 
 File: dash.info,  Node: Contributors,  Prev: Contribute,  Up: Development
 
 3.2 Contributors
 ================
 
    • Matus Goljer (https://github.com/Fuco1) contributed lots of
      features and functions.
    • Takafumi Arakaki (https://github.com/tkf) contributed ‘-group-by’.
    • tali713 (https://github.com/tali713) is the author of ‘-applify’.
    • Víctor M. Valenzuela (https://github.com/vemv) contributed
      ‘-repeat’.
    • Nic Ferrier (https://github.com/nicferrier) contributed ‘-cons*’.
    • Wilfred Hughes (https://github.com/Wilfred) contributed ‘-slice’,
      ‘-first-item’, and ‘-last-item’.
    • Emanuel Evans (https://github.com/shosti) contributed ‘-if-let’,
      ‘-when-let’, and ‘-insert-at’.
    • Johan Andersson (https://github.com/rejeep) contributed ‘-sum’,
      ‘-product’, and ‘-same-items?’.
    • Christina Whyte (https://github.com/kurisuwhyte) contributed
      ‘-compose’.
    • Steve Lamb (https://github.com/steventlamb) contributed ‘-cycle’,
      ‘-pad’, ‘-annotate’, ‘-zip-fill’, and a variadic version of ‘-zip’.
    • Fredrik Bergroth (https://github.com/fbergroth) made the ‘-if-let’
      family use ‘-let’ destructuring and improved the script for
      generating documentation.
    • Mark Oteiza (https://github.com/holomorph) contributed ‘-iota’ and
      the script to create an Info manual.
    • Vasilij Schneidermann (https://github.com/wasamasa) contributed
      ‘-some’.
    • William West (https://github.com/occidens) made ‘-fixfn’ more
      robust at handling floats.
    • Cam Saul (https://github.com/camsaul) contributed ‘-some->’,
      ‘-some->>’, and ‘-some-->’.
    • Basil L. Contovounesios (https://github.com/basil-conto)
      contributed ‘-common-prefix’, ‘-common-suffix’, and various other
      improvements.
    • Paul Pogonyshev (https://github.com/doublep) contributed ‘-each-r’
      and ‘-each-r-while’.
 
    Thanks!
 
    New contributors are very welcome.  *Note Contribute::.
 
 
 File: dash.info,  Node: FDL,  Next: GPL,  Prev: Development,  Up: Top
 
 Appendix A GNU Free Documentation License
 *****************************************
 
                      Version 1.3, 3 November 2008
 
      Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
      <https://fsf.org/>
 
      Everyone is permitted to copy and distribute verbatim copies
      of this license document, but changing it is not allowed.
 
   0. PREAMBLE
 
      The purpose of this License is to make a manual, textbook, or other
      functional and useful document “free” in the sense of freedom: to
      assure everyone the effective freedom to copy and redistribute it,
      with or without modifying it, either commercially or
      noncommercially.  Secondarily, this License preserves for the
      author and publisher a way to get credit for their work, while not
      being considered responsible for modifications made by others.
 
      This License is a kind of “copyleft”, which means that derivative
      works of the document must themselves be free in the same sense.
      It complements the GNU General Public License, which is a copyleft
      license designed for free software.
 
      We have designed this License in order to use it for manuals for
      free software, because free software needs free documentation: a
      free program should come with manuals providing the same freedoms
      that the software does.  But this License is not limited to
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      of subject matter or whether it is published as a printed book.  We
      recommend this License principally for works whose purpose is
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      A “Modified Version” of the Document means any work containing the
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           “Endorsements” or to conflict in title with any Invariant
           Section.
 
        O. Preserve any Warranty Disclaimers.
 
      If the Modified Version includes new front-matter sections or
      appendices that qualify as Secondary Sections and contain no
      material copied from the Document, you may at your option designate
      some or all of these sections as invariant.  To do this, add their
      titles to the list of Invariant Sections in the Modified Version’s
      license notice.  These titles must be distinct from any other
      section titles.
 
      You may add a section Entitled “Endorsements”, provided it contains
      nothing but endorsements of your Modified Version by various
      parties—for example, statements of peer review or that the text has
      been approved by an organization as the authoritative definition of
      a standard.
 
      You may add a passage of up to five words as a Front-Cover Text,
      and a passage of up to 25 words as a Back-Cover Text, to the end of
      the list of Cover Texts in the Modified Version.  Only one passage
      of Front-Cover Text and one of Back-Cover Text may be added by (or
      through arrangements made by) any one entity.  If the Document
      already includes a cover text for the same cover, previously added
      by you or by arrangement made by the same entity you are acting on
      behalf of, you may not add another; but you may replace the old
      one, on explicit permission from the previous publisher that added
      the old one.
 
      The author(s) and publisher(s) of the Document do not by this
      License give permission to use their names for publicity for or to
      assert or imply endorsement of any Modified Version.
 
   5. COMBINING DOCUMENTS
 
      You may combine the Document with other documents released under
      this License, under the terms defined in section 4 above for
      modified versions, provided that you include in the combination all
      of the Invariant Sections of all of the original documents,
      unmodified, and list them all as Invariant Sections of your
      combined work in its license notice, and that you preserve all
      their Warranty Disclaimers.
 
      The combined work need only contain one copy of this License, and
      multiple identical Invariant Sections may be replaced with a single
      copy.  If there are multiple Invariant Sections with the same name
      but different contents, make the title of each such section unique
      by adding at the end of it, in parentheses, the name of the
      original author or publisher of that section if known, or else a
      unique number.  Make the same adjustment to the section titles in
      the list of Invariant Sections in the license notice of the
      combined work.
 
      In the combination, you must combine any sections Entitled
      “History” in the various original documents, forming one section
      Entitled “History”; likewise combine any sections Entitled
      “Acknowledgements”, and any sections Entitled “Dedications”.  You
      must delete all sections Entitled “Endorsements.”
 
   6. COLLECTIONS OF DOCUMENTS
 
      You may make a collection consisting of the Document and other
      documents released under this License, and replace the individual
      copies of this License in the various documents with a single copy
      that is included in the collection, provided that you follow the
      rules of this License for verbatim copying of each of the documents
      in all other respects.
 
      You may extract a single document from such a collection, and
      distribute it individually under this License, provided you insert
      a copy of this License into the extracted document, and follow this
      License in all other respects regarding verbatim copying of that
      document.
 
   7. AGGREGATION WITH INDEPENDENT WORKS
 
      A compilation of the Document or its derivatives with other
      separate and independent documents or works, in or on a volume of a
      storage or distribution medium, is called an “aggregate” if the
      copyright resulting from the compilation is not used to limit the
      legal rights of the compilation’s users beyond what the individual
      works permit.  When the Document is included in an aggregate, this
      License does not apply to the other works in the aggregate which
      are not themselves derivative works of the Document.
 
      If the Cover Text requirement of section 3 is applicable to these
      copies of the Document, then if the Document is less than one half
      of the entire aggregate, the Document’s Cover Texts may be placed
      on covers that bracket the Document within the aggregate, or the
      electronic equivalent of covers if the Document is in electronic
      form.  Otherwise they must appear on printed covers that bracket
      the whole aggregate.
 
   8. TRANSLATION
 
      Translation is considered a kind of modification, so you may
      distribute translations of the Document under the terms of section
      4.  Replacing Invariant Sections with translations requires special
      permission from their copyright holders, but you may include
      translations of some or all Invariant Sections in addition to the
      original versions of these Invariant Sections.  You may include a
      translation of this License, and all the license notices in the
      Document, and any Warranty Disclaimers, provided that you also
      include the original English version of this License and the
      original versions of those notices and disclaimers.  In case of a
      disagreement between the translation and the original version of
      this License or a notice or disclaimer, the original version will
      prevail.
 
      If a section in the Document is Entitled “Acknowledgements”,
      “Dedications”, or “History”, the requirement (section 4) to
      Preserve its Title (section 1) will typically require changing the
      actual title.
 
   9. TERMINATION
 
      You may not copy, modify, sublicense, or distribute the Document
      except as expressly provided under this License.  Any attempt
      otherwise to copy, modify, sublicense, or distribute it is void,
      and will automatically terminate your rights under this License.
 
      However, if you cease all violation of this License, then your
      license from a particular copyright holder is reinstated (a)
      provisionally, unless and until the copyright holder explicitly and
      finally terminates your license, and (b) permanently, if the
      copyright holder fails to notify you of the violation by some
      reasonable means prior to 60 days after the cessation.
 
      Moreover, your license from a particular copyright holder is
      reinstated permanently if the copyright holder notifies you of the
      violation by some reasonable means, this is the first time you have
      received notice of violation of this License (for any work) from
      that copyright holder, and you cure the violation prior to 30 days
      after your receipt of the notice.
 
      Termination of your rights under this section does not terminate
      the licenses of parties who have received copies or rights from you
      under this License.  If your rights have been terminated and not
      permanently reinstated, receipt of a copy of some or all of the
      same material does not give you any rights to use it.
 
   10. FUTURE REVISIONS OF THIS LICENSE
 
      The Free Software Foundation may publish new, revised versions of
      the GNU Free Documentation License from time to time.  Such new
      versions will be similar in spirit to the present version, but may
      differ in detail to address new problems or concerns.  See
      <https://www.gnu.org/licenses/>.
 
      Each version of the License is given a distinguishing version
      number.  If the Document specifies that a particular numbered
      version of this License “or any later version” applies to it, you
      have the option of following the terms and conditions either of
      that specified version or of any later version that has been
      published (not as a draft) by the Free Software Foundation.  If the
      Document does not specify a version number of this License, you may
      choose any version ever published (not as a draft) by the Free
      Software Foundation.  If the Document specifies that a proxy can
      decide which future versions of this License can be used, that
      proxy’s public statement of acceptance of a version permanently
      authorizes you to choose that version for the Document.
 
   11. RELICENSING
 
      “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any
      World Wide Web server that publishes copyrightable works and also
      provides prominent facilities for anybody to edit those works.  A
      public wiki that anybody can edit is an example of such a server.
      A “Massive Multiauthor Collaboration” (or “MMC”) contained in the
      site means any set of copyrightable works thus published on the MMC
      site.
 
      “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0
      license published by Creative Commons Corporation, a not-for-profit
      corporation with a principal place of business in San Francisco,
      California, as well as future copyleft versions of that license
      published by that same organization.
 
      “Incorporate” means to publish or republish a Document, in whole or
      in part, as part of another Document.
 
      An MMC is “eligible for relicensing” if it is licensed under this
      License, and if all works that were first published under this
      License somewhere other than this MMC, and subsequently
      incorporated in whole or in part into the MMC, (1) had no cover
      texts or invariant sections, and (2) were thus incorporated prior
      to November 1, 2008.
 
      The operator of an MMC Site may republish an MMC contained in the
      site under CC-BY-SA on the same site at any time before August 1,
      2009, provided the MMC is eligible for relicensing.
 
 ADDENDUM: How to use this License for your documents
 ====================================================
 
 To use this License in a document you have written, include a copy of
 the License in the document and put the following copyright and license
 notices just after the title page:
 
        Copyright (C)  YEAR  YOUR NAME.
        Permission is granted to copy, distribute and/or modify this document
        under the terms of the GNU Free Documentation License, Version 1.3
        or any later version published by the Free Software Foundation;
        with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
        Texts.  A copy of the license is included in the section entitled ``GNU
        Free Documentation License''.
 
    If you have Invariant Sections, Front-Cover Texts and Back-Cover
 Texts, replace the “with...Texts.” line with this:
 
          with the Invariant Sections being LIST THEIR TITLES, with
          the Front-Cover Texts being LIST, and with the Back-Cover Texts
          being LIST.
 
    If you have Invariant Sections without Cover Texts, or some other
 combination of the three, merge those two alternatives to suit the
 situation.
 
    If your document contains nontrivial examples of program code, we
 recommend releasing these examples in parallel under your choice of free
 software license, such as the GNU General Public License, to permit
 their use in free software.
 
 
 File: dash.info,  Node: GPL,  Next: Index,  Prev: FDL,  Up: Top
 
 Appendix B GNU General Public License
 *************************************
 
                         Version 3, 29 June 2007
 
      Copyright © 2007 Free Software Foundation, Inc. <https://fsf.org/>
 
      Everyone is permitted to copy and distribute verbatim copies of this
      license document, but changing it is not allowed.
 
 Preamble
 ========
 
 The GNU General Public License is a free, copyleft license for software
 and other kinds of works.
 
    The licenses for most software and other practical works are designed
 to take away your freedom to share and change the works.  By contrast,
 the GNU General Public License is intended to guarantee your freedom to
 share and change all versions of a program—to make sure it remains free
 software for all its users.  We, the Free Software Foundation, use the
 GNU General Public License for most of our software; it applies also to
 any other work released this way by its authors.  You can apply it to
 your programs, too.
 
    When we speak of free software, we are referring to freedom, not
 price.  Our General Public Licenses are designed to make sure that you
 have the freedom to distribute copies of free software (and charge for
 them if you wish), that you receive source code or can get it if you
 want it, that you can change the software or use pieces of it in new
 free programs, and that you know you can do these things.
 
    To protect your rights, we need to prevent others from denying you
 these rights or asking you to surrender the rights.  Therefore, you have
 certain responsibilities if you distribute copies of the software, or if
 you modify it: responsibilities to respect the freedom of others.
 
    For example, if you distribute copies of such a program, whether
 gratis or for a fee, you must pass on to the recipients the same
 freedoms that you received.  You must make sure that they, too, receive
 or can get the source code.  And you must show them these terms so they
 know their rights.
 
    Developers that use the GNU GPL protect your rights with two steps:
 (1) assert copyright on the software, and (2) offer you this License
 giving you legal permission to copy, distribute and/or modify it.
 
    For the developers’ and authors’ protection, the GPL clearly explains
 that there is no warranty for this free software.  For both users’ and
 authors’ sake, the GPL requires that modified versions be marked as
 changed, so that their problems will not be attributed erroneously to
 authors of previous versions.
 
    Some devices are designed to deny users access to install or run
 modified versions of the software inside them, although the manufacturer
 can do so.  This is fundamentally incompatible with the aim of
 protecting users’ freedom to change the software.  The systematic
 pattern of such abuse occurs in the area of products for individuals to
 use, which is precisely where it is most unacceptable.  Therefore, we
 have designed this version of the GPL to prohibit the practice for those
 products.  If such problems arise substantially in other domains, we
 stand ready to extend this provision to those domains in future versions
 of the GPL, as needed to protect the freedom of users.
 
    Finally, every program is threatened constantly by software patents.
 States should not allow patents to restrict development and use of
 software on general-purpose computers, but in those that do, we wish to
 avoid the special danger that patents applied to a free program could
 make it effectively proprietary.  To prevent this, the GPL assures that
 patents cannot be used to render the program non-free.
 
    The precise terms and conditions for copying, distribution and
 modification follow.
 
 TERMS AND CONDITIONS
 ====================
 
   0. Definitions.
 
      “This License” refers to version 3 of the GNU General Public
      License.
 
      “Copyright” also means copyright-like laws that apply to other
      kinds of works, such as semiconductor masks.
 
      “The Program” refers to any copyrightable work licensed under this
      License.  Each licensee is addressed as “you”.  “Licensees” and
      “recipients” may be individuals or organizations.
 
      To “modify” a work means to copy from or adapt all or part of the
      work in a fashion requiring copyright permission, other than the
      making of an exact copy.  The resulting work is called a “modified
      version” of the earlier work or a work “based on” the earlier work.
 
      A “covered work” means either the unmodified Program or a work
      based on the Program.
 
      To “propagate” a work means to do anything with it that, without
      permission, would make you directly or secondarily liable for
      infringement under applicable copyright law, except executing it on
      a computer or modifying a private copy.  Propagation includes
      copying, distribution (with or without modification), making
      available to the public, and in some countries other activities as
      well.
 
      To “convey” a work means any kind of propagation that enables other
      parties to make or receive copies.  Mere interaction with a user
      through a computer network, with no transfer of a copy, is not
      conveying.
 
      An interactive user interface displays “Appropriate Legal Notices”
      to the extent that it includes a convenient and prominently visible
      feature that (1) displays an appropriate copyright notice, and (2)
      tells the user that there is no warranty for the work (except to
      the extent that warranties are provided), that licensees may convey
      the work under this License, and how to view a copy of this
      License.  If the interface presents a list of user commands or
      options, such as a menu, a prominent item in the list meets this
      criterion.
 
   1. Source Code.
 
      The “source code” for a work means the preferred form of the work
      for making modifications to it.  “Object code” means any non-source
      form of a work.
 
      A “Standard Interface” means an interface that either is an
      official standard defined by a recognized standards body, or, in
      the case of interfaces specified for a particular programming
      language, one that is widely used among developers working in that
      language.
 
      The “System Libraries” of an executable work include anything,
      other than the work as a whole, that (a) is included in the normal
      form of packaging a Major Component, but which is not part of that
      Major Component, and (b) serves only to enable use of the work with
      that Major Component, or to implement a Standard Interface for
      which an implementation is available to the public in source code
      form.  A “Major Component”, in this context, means a major
      essential component (kernel, window system, and so on) of the
      specific operating system (if any) on which the executable work
      runs, or a compiler used to produce the work, or an object code
      interpreter used to run it.
 
      The “Corresponding Source” for a work in object code form means all
      the source code needed to generate, install, and (for an executable
      work) run the object code and to modify the work, including scripts
      to control those activities.  However, it does not include the
      work’s System Libraries, or general-purpose tools or generally
      available free programs which are used unmodified in performing
      those activities but which are not part of the work.  For example,
      Corresponding Source includes interface definition files associated
      with source files for the work, and the source code for shared
      libraries and dynamically linked subprograms that the work is
      specifically designed to require, such as by intimate data
      communication or control flow between those subprograms and other
      parts of the work.
 
      The Corresponding Source need not include anything that users can
      regenerate automatically from other parts of the Corresponding
      Source.
 
      The Corresponding Source for a work in source code form is that
      same work.
 
   2. Basic Permissions.
 
      All rights granted under this License are granted for the term of
      copyright on the Program, and are irrevocable provided the stated
      conditions are met.  This License explicitly affirms your unlimited
      permission to run the unmodified Program.  The output from running
      a covered work is covered by this License only if the output, given
      its content, constitutes a covered work.  This License acknowledges
      your rights of fair use or other equivalent, as provided by
      copyright law.
 
      You may make, run and propagate covered works that you do not
      convey, without conditions so long as your license otherwise
      remains in force.  You may convey covered works to others for the
      sole purpose of having them make modifications exclusively for you,
      or provide you with facilities for running those works, provided
      that you comply with the terms of this License in conveying all
      material for which you do not control copyright.  Those thus making
      or running the covered works for you must do so exclusively on your
      behalf, under your direction and control, on terms that prohibit
      them from making any copies of your copyrighted material outside
      their relationship with you.
 
      Conveying under any other circumstances is permitted solely under
      the conditions stated below.  Sublicensing is not allowed; section
      10 makes it unnecessary.
 
   3. Protecting Users’ Legal Rights From Anti-Circumvention Law.
 
      No covered work shall be deemed part of an effective technological
      measure under any applicable law fulfilling obligations under
      article 11 of the WIPO copyright treaty adopted on 20 December
      1996, or similar laws prohibiting or restricting circumvention of
      such measures.
 
      When you convey a covered work, you waive any legal power to forbid
      circumvention of technological measures to the extent such
      circumvention is effected by exercising rights under this License
      with respect to the covered work, and you disclaim any intention to
      limit operation or modification of the work as a means of
      enforcing, against the work’s users, your or third parties’ legal
      rights to forbid circumvention of technological measures.
 
   4. Conveying Verbatim Copies.
 
      You may convey verbatim copies of the Program’s source code as you
      receive it, in any medium, provided that you conspicuously and
      appropriately publish on each copy an appropriate copyright notice;
      keep intact all notices stating that this License and any
      non-permissive terms added in accord with section 7 apply to the
      code; keep intact all notices of the absence of any warranty; and
      give all recipients a copy of this License along with the Program.
 
      You may charge any price or no price for each copy that you convey,
      and you may offer support or warranty protection for a fee.
 
   5. Conveying Modified Source Versions.
 
      You may convey a work based on the Program, or the modifications to
      produce it from the Program, in the form of source code under the
      terms of section 4, provided that you also meet all of these
      conditions:
 
        a. The work must carry prominent notices stating that you
           modified it, and giving a relevant date.
 
        b. The work must carry prominent notices stating that it is
           released under this License and any conditions added under
           section 7.  This requirement modifies the requirement in
           section 4 to “keep intact all notices”.
 
        c. You must license the entire work, as a whole, under this
           License to anyone who comes into possession of a copy.  This
           License will therefore apply, along with any applicable
           section 7 additional terms, to the whole of the work, and all
           its parts, regardless of how they are packaged.  This License
           gives no permission to license the work in any other way, but
           it does not invalidate such permission if you have separately
           received it.
 
        d. If the work has interactive user interfaces, each must display
           Appropriate Legal Notices; however, if the Program has
           interactive interfaces that do not display Appropriate Legal
           Notices, your work need not make them do so.
 
      A compilation of a covered work with other separate and independent
      works, which are not by their nature extensions of the covered
      work, and which are not combined with it such as to form a larger
      program, in or on a volume of a storage or distribution medium, is
      called an “aggregate” if the compilation and its resulting
      copyright are not used to limit the access or legal rights of the
      compilation’s users beyond what the individual works permit.
      Inclusion of a covered work in an aggregate does not cause this
      License to apply to the other parts of the aggregate.
 
   6. Conveying Non-Source Forms.
 
      You may convey a covered work in object code form under the terms
      of sections 4 and 5, provided that you also convey the
      machine-readable Corresponding Source under the terms of this
      License, in one of these ways:
 
        a. Convey the object code in, or embodied in, a physical product
           (including a physical distribution medium), accompanied by the
           Corresponding Source fixed on a durable physical medium
           customarily used for software interchange.
 
        b. Convey the object code in, or embodied in, a physical product
           (including a physical distribution medium), accompanied by a
           written offer, valid for at least three years and valid for as
           long as you offer spare parts or customer support for that
           product model, to give anyone who possesses the object code
           either (1) a copy of the Corresponding Source for all the
           software in the product that is covered by this License, on a
           durable physical medium customarily used for software
           interchange, for a price no more than your reasonable cost of
           physically performing this conveying of source, or (2) access
           to copy the Corresponding Source from a network server at no
           charge.
 
        c. Convey individual copies of the object code with a copy of the
           written offer to provide the Corresponding Source.  This
           alternative is allowed only occasionally and noncommercially,
           and only if you received the object code with such an offer,
           in accord with subsection 6b.
 
        d. Convey the object code by offering access from a designated
           place (gratis or for a charge), and offer equivalent access to
           the Corresponding Source in the same way through the same
           place at no further charge.  You need not require recipients
           to copy the Corresponding Source along with the object code.
           If the place to copy the object code is a network server, the
           Corresponding Source may be on a different server (operated by
           you or a third party) that supports equivalent copying
           facilities, provided you maintain clear directions next to the
           object code saying where to find the Corresponding Source.
           Regardless of what server hosts the Corresponding Source, you
           remain obligated to ensure that it is available for as long as
           needed to satisfy these requirements.
 
        e. Convey the object code using peer-to-peer transmission,
           provided you inform other peers where the object code and
           Corresponding Source of the work are being offered to the
           general public at no charge under subsection 6d.
 
      A separable portion of the object code, whose source code is
      excluded from the Corresponding Source as a System Library, need
      not be included in conveying the object code work.
 
      A “User Product” is either (1) a “consumer product”, which means
      any tangible personal property which is normally used for personal,
      family, or household purposes, or (2) anything designed or sold for
      incorporation into a dwelling.  In determining whether a product is
      a consumer product, doubtful cases shall be resolved in favor of
      coverage.  For a particular product received by a particular user,
      “normally used” refers to a typical or common use of that class of
      product, regardless of the status of the particular user or of the
      way in which the particular user actually uses, or expects or is
      expected to use, the product.  A product is a consumer product
      regardless of whether the product has substantial commercial,
      industrial or non-consumer uses, unless such uses represent the
      only significant mode of use of the product.
 
      “Installation Information” for a User Product means any methods,
      procedures, authorization keys, or other information required to
      install and execute modified versions of a covered work in that
      User Product from a modified version of its Corresponding Source.
      The information must suffice to ensure that the continued
      functioning of the modified object code is in no case prevented or
      interfered with solely because modification has been made.
 
      If you convey an object code work under this section in, or with,
      or specifically for use in, a User Product, and the conveying
      occurs as part of a transaction in which the right of possession
      and use of the User Product is transferred to the recipient in
      perpetuity or for a fixed term (regardless of how the transaction
      is characterized), the Corresponding Source conveyed under this
      section must be accompanied by the Installation Information.  But
      this requirement does not apply if neither you nor any third party
      retains the ability to install modified object code on the User
      Product (for example, the work has been installed in ROM).
 
      The requirement to provide Installation Information does not
      include a requirement to continue to provide support service,
      warranty, or updates for a work that has been modified or installed
      by the recipient, or for the User Product in which it has been
      modified or installed.  Access to a network may be denied when the
      modification itself materially and adversely affects the operation
      of the network or violates the rules and protocols for
      communication across the network.
 
      Corresponding Source conveyed, and Installation Information
      provided, in accord with this section must be in a format that is
      publicly documented (and with an implementation available to the
      public in source code form), and must require no special password
      or key for unpacking, reading or copying.
 
   7. Additional Terms.
 
      “Additional permissions” are terms that supplement the terms of
      this License by making exceptions from one or more of its
      conditions.  Additional permissions that are applicable to the
      entire Program shall be treated as though they were included in
      this License, to the extent that they are valid under applicable
      law.  If additional permissions apply only to part of the Program,
      that part may be used separately under those permissions, but the
      entire Program remains governed by this License without regard to
      the additional permissions.
 
      When you convey a copy of a covered work, you may at your option
      remove any additional permissions from that copy, or from any part
      of it.  (Additional permissions may be written to require their own
      removal in certain cases when you modify the work.)  You may place
      additional permissions on material, added by you to a covered work,
      for which you have or can give appropriate copyright permission.
 
      Notwithstanding any other provision of this License, for material
      you add to a covered work, you may (if authorized by the copyright
      holders of that material) supplement the terms of this License with
      terms:
 
        a. Disclaiming warranty or limiting liability differently from
           the terms of sections 15 and 16 of this License; or
 
        b. Requiring preservation of specified reasonable legal notices
           or author attributions in that material or in the Appropriate
           Legal Notices displayed by works containing it; or
 
        c. Prohibiting misrepresentation of the origin of that material,
           or requiring that modified versions of such material be marked
           in reasonable ways as different from the original version; or
 
        d. Limiting the use for publicity purposes of names of licensors
           or authors of the material; or
 
        e. Declining to grant rights under trademark law for use of some
           trade names, trademarks, or service marks; or
 
        f. Requiring indemnification of licensors and authors of that
           material by anyone who conveys the material (or modified
           versions of it) with contractual assumptions of liability to
           the recipient, for any liability that these contractual
           assumptions directly impose on those licensors and authors.
 
      All other non-permissive additional terms are considered “further
      restrictions” within the meaning of section 10.  If the Program as
      you received it, or any part of it, contains a notice stating that
      it is governed by this License along with a term that is a further
      restriction, you may remove that term.  If a license document
      contains a further restriction but permits relicensing or conveying
      under this License, you may add to a covered work material governed
      by the terms of that license document, provided that the further
      restriction does not survive such relicensing or conveying.
 
      If you add terms to a covered work in accord with this section, you
      must place, in the relevant source files, a statement of the
      additional terms that apply to those files, or a notice indicating
      where to find the applicable terms.
 
      Additional terms, permissive or non-permissive, may be stated in
      the form of a separately written license, or stated as exceptions;
      the above requirements apply either way.
 
   8. Termination.
 
      You may not propagate or modify a covered work except as expressly
      provided under this License.  Any attempt otherwise to propagate or
      modify it is void, and will automatically terminate your rights
      under this License (including any patent licenses granted under the
      third paragraph of section 11).
 
      However, if you cease all violation of this License, then your
      license from a particular copyright holder is reinstated (a)
      provisionally, unless and until the copyright holder explicitly and
      finally terminates your license, and (b) permanently, if the
      copyright holder fails to notify you of the violation by some
      reasonable means prior to 60 days after the cessation.
 
      Moreover, your license from a particular copyright holder is
      reinstated permanently if the copyright holder notifies you of the
      violation by some reasonable means, this is the first time you have
      received notice of violation of this License (for any work) from
      that copyright holder, and you cure the violation prior to 30 days
      after your receipt of the notice.
 
      Termination of your rights under this section does not terminate
      the licenses of parties who have received copies or rights from you
      under this License.  If your rights have been terminated and not
      permanently reinstated, you do not qualify to receive new licenses
      for the same material under section 10.
 
   9. Acceptance Not Required for Having Copies.
 
      You are not required to accept this License in order to receive or
      run a copy of the Program.  Ancillary propagation of a covered work
      occurring solely as a consequence of using peer-to-peer
      transmission to receive a copy likewise does not require
      acceptance.  However, nothing other than this License grants you
      permission to propagate or modify any covered work.  These actions
      infringe copyright if you do not accept this License.  Therefore,
      by modifying or propagating a covered work, you indicate your
      acceptance of this License to do so.
 
   10. Automatic Licensing of Downstream Recipients.
 
      Each time you convey a covered work, the recipient automatically
      receives a license from the original licensors, to run, modify and
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      responsible for enforcing compliance by third parties with this
      License.
 
      An “entity transaction” is a transaction transferring control of an
      organization, or substantially all assets of one, or subdividing an
      organization, or merging organizations.  If propagation of a
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      of the Corresponding Source of the work from the predecessor in
      interest, if the predecessor has it or can get it with reasonable
      efforts.
 
      You may not impose any further restrictions on the exercise of the
      rights granted or affirmed under this License.  For example, you
      may not impose a license fee, royalty, or other charge for exercise
      of rights granted under this License, and you may not initiate
      litigation (including a cross-claim or counterclaim in a lawsuit)
      alleging that any patent claim is infringed by making, using,
      selling, offering for sale, or importing the Program or any portion
      of it.
 
   11. Patents.
 
      A “contributor” is a copyright holder who authorizes use under this
      License of the Program or a work on which the Program is based.
      The work thus licensed is called the contributor’s “contributor
      version”.
 
      A contributor’s “essential patent claims” are all patent claims
      owned or controlled by the contributor, whether already acquired or
      hereafter acquired, that would be infringed by some manner,
      permitted by this License, of making, using, or selling its
      contributor version, but do not include claims that would be
      infringed only as a consequence of further modification of the
      contributor version.  For purposes of this definition, “control”
      includes the right to grant patent sublicenses in a manner
      consistent with the requirements of this License.
 
      Each contributor grants you a non-exclusive, worldwide,
      royalty-free patent license under the contributor’s essential
      patent claims, to make, use, sell, offer for sale, import and
      otherwise run, modify and propagate the contents of its contributor
      version.
 
      In the following three paragraphs, a “patent license” is any
      express agreement or commitment, however denominated, not to
      enforce a patent (such as an express permission to practice a
      patent or covenant not to sue for patent infringement).  To “grant”
      such a patent license to a party means to make such an agreement or
      commitment not to enforce a patent against the party.
 
      If you convey a covered work, knowingly relying on a patent
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      Corresponding Source to be so available, or (2) arrange to deprive
      yourself of the benefit of the patent license for this particular
      work, or (3) arrange, in a manner consistent with the requirements
      of this License, to extend the patent license to downstream
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      that, but for the patent license, your conveying the covered work
      in a country, or your recipient’s use of the covered work in a
      country, would infringe one or more identifiable patents in that
      country that you have reason to believe are valid.
 
      If, pursuant to or in connection with a single transaction or
      arrangement, you convey, or propagate by procuring conveyance of, a
      covered work, and grant a patent license to some of the parties
      receiving the covered work authorizing them to use, propagate,
      modify or convey a specific copy of the covered work, then the
      patent license you grant is automatically extended to all
      recipients of the covered work and works based on it.
 
      A patent license is “discriminatory” if it does not include within
      the scope of its coverage, prohibits the exercise of, or is
      conditioned on the non-exercise of one or more of the rights that
      are specifically granted under this License.  You may not convey a
      covered work if you are a party to an arrangement with a third
      party that is in the business of distributing software, under which
      you make payment to the third party based on the extent of your
      activity of conveying the work, and under which the third party
      grants, to any of the parties who would receive the covered work
      from you, a discriminatory patent license (a) in connection with
      copies of the covered work conveyed by you (or copies made from
      those copies), or (b) primarily for and in connection with specific
      products or compilations that contain the covered work, unless you
      entered into that arrangement, or that patent license was granted,
      prior to 28 March 2007.
 
      Nothing in this License shall be construed as excluding or limiting
      any implied license or other defenses to infringement that may
      otherwise be available to you under applicable patent law.
 
   12. No Surrender of Others’ Freedom.
 
      If conditions are imposed on you (whether by court order, agreement
      or otherwise) that contradict the conditions of this License, they
      do not excuse you from the conditions of this License.  If you
      cannot convey a covered work so as to satisfy simultaneously your
      obligations under this License and any other pertinent obligations,
      then as a consequence you may not convey it at all.  For example,
      if you agree to terms that obligate you to collect a royalty for
      further conveying from those to whom you convey the Program, the
      only way you could satisfy both those terms and this License would
      be to refrain entirely from conveying the Program.
 
   13. Use with the GNU Affero General Public License.
 
      Notwithstanding any other provision of this License, you have
      permission to link or combine any covered work with a work licensed
      under version 3 of the GNU Affero General Public License into a
      single combined work, and to convey the resulting work.  The terms
      of this License will continue to apply to the part which is the
      covered work, but the special requirements of the GNU Affero
      General Public License, section 13, concerning interaction through
      a network will apply to the combination as such.
 
   14. Revised Versions of this License.
 
      The Free Software Foundation may publish revised and/or new
      versions of the GNU General Public License from time to time.  Such
      new versions will be similar in spirit to the present version, but
      may differ in detail to address new problems or concerns.
 
      Each version is given a distinguishing version number.  If the
      Program specifies that a certain numbered version of the GNU
      General Public License “or any later version” applies to it, you
      have the option of following the terms and conditions either of
      that numbered version or of any later version published by the Free
      Software Foundation.  If the Program does not specify a version
      number of the GNU General Public License, you may choose any
      version ever published by the Free Software Foundation.
 
      If the Program specifies that a proxy can decide which future
      versions of the GNU General Public License can be used, that
      proxy’s public statement of acceptance of a version permanently
      authorizes you to choose that version for the Program.
 
      Later license versions may give you additional or different
      permissions.  However, no additional obligations are imposed on any
      author or copyright holder as a result of your choosing to follow a
      later version.
 
   15. Disclaimer of Warranty.
 
      THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
      APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE
      COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS”
      WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
      INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
      MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE
      RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.
      SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
      NECESSARY SERVICING, REPAIR OR CORRECTION.
 
   16. Limitation of Liability.
 
      IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
      WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES
      AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR
      DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
      CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
      THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA
      BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
      PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
      PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF
      THE POSSIBILITY OF SUCH DAMAGES.
 
   17. Interpretation of Sections 15 and 16.
 
      If the disclaimer of warranty and limitation of liability provided
      above cannot be given local legal effect according to their terms,
      reviewing courts shall apply local law that most closely
      approximates an absolute waiver of all civil liability in
      connection with the Program, unless a warranty or assumption of
      liability accompanies a copy of the Program in return for a fee.
 
 END OF TERMS AND CONDITIONS
 ===========================
 
 How to Apply These Terms to Your New Programs
 =============================================
 
 If you develop a new program, and you want it to be of the greatest
 possible use to the public, the best way to achieve this is to make it
 free software which everyone can redistribute and change under these
 terms.
 
    To do so, attach the following notices to the program.  It is safest
 to attach them to the start of each source file to most effectively
 state the exclusion of warranty; and each file should have at least the
 “copyright” line and a pointer to where the full notice is found.
 
      ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES.
      Copyright (C) YEAR NAME OF AUTHOR
 
      This program is free software: you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation, either version 3 of the License, or (at
      your option) any later version.
 
      This program is distributed in the hope that it will be useful, but
      WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      General Public License for more details.
 
      You should have received a copy of the GNU General Public License
      along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
    Also add information on how to contact you by electronic and paper
 mail.
 
    If the program does terminal interaction, make it output a short
 notice like this when it starts in an interactive mode:
 
      PROGRAM Copyright (C) YEAR NAME OF AUTHOR
      This program comes with ABSOLUTELY NO WARRANTY; for details type ‘show w’.
      This is free software, and you are welcome to redistribute it
      under certain conditions; type ‘show c’ for details.
 
    The hypothetical commands ‘show w’ and ‘show c’ should show the
 appropriate parts of the General Public License.  Of course, your
 program’s commands might be different; for a GUI interface, you would
 use an “about box”.
 
    You should also get your employer (if you work as a programmer) or
 school, if any, to sign a “copyright disclaimer” for the program, if
 necessary.  For more information on this, and how to apply and follow
 the GNU GPL, see <https://www.gnu.org/licenses/>.
 
    The GNU General Public License does not permit incorporating your
 program into proprietary programs.  If your program is a subroutine
 library, you may consider it more useful to permit linking proprietary
 applications with the library.  If this is what you want to do, use the
 GNU Lesser General Public License instead of this License.  But first,
 please read <https://www.gnu.org/licenses/why-not-lgpl.html>.
 
 
 File: dash.info,  Node: Index,  Prev: GPL,  Up: Top
 
 Index
 *****
 
 
 * Menu:
 
 * !cdr:                                  Destructive operations.
                                                               (line  16)
 * !cons:                                 Destructive operations.
                                                               (line   8)
 * -->:                                   Threading macros.    (line  35)
 * ->:                                    Threading macros.    (line   9)
 * ->>:                                   Threading macros.    (line  22)
 * -all?:                                 Predicates.          (line  53)
 * -andfn:                                Function combinators.
                                                               (line 184)
 * -annotate:                             Maps.                (line  84)
 * -any?:                                 Predicates.          (line  41)
 * -applify:                              Function combinators.
                                                               (line  63)
 * -as->:                                 Threading macros.    (line  49)
 * -butlast:                              Other list operations.
                                                               (line 335)
 * -clone:                                Tree operations.     (line 122)
 * -common-prefix:                        Reductions.          (line 242)
 * -common-suffix:                        Reductions.          (line 252)
 * -compose:                              Function combinators.
                                                               (line  49)
 * -concat:                               List to list.        (line  23)
 * -cons*:                                Other list operations.
                                                               (line  30)
 * -cons-pair?:                           Predicates.          (line 167)
 * -const:                                Function combinators.
                                                               (line 128)
 * -contains?:                            Predicates.          (line 100)
 * -copy:                                 Maps.                (line 139)
 * -count:                                Reductions.          (line 172)
 * -cut:                                  Function combinators.
                                                               (line 140)
 * -cycle:                                Other list operations.
                                                               (line 180)
 * -difference:                           Set operations.      (line  20)
 * -distinct:                             Set operations.      (line  62)
 * -dotimes:                              Side effects.        (line  80)
 * -doto:                                 Threading macros.    (line  99)
 * -drop:                                 Sublist selection.   (line 147)
 * -drop-last:                            Sublist selection.   (line 161)
 * -drop-while:                           Sublist selection.   (line 192)
 * -each:                                 Side effects.        (line   8)
 * -each-indexed:                         Side effects.        (line  38)
 * -each-r:                               Side effects.        (line  52)
 * -each-r-while:                         Side effects.        (line  65)
 * -each-while:                           Side effects.        (line  24)
 * -elem-index:                           Indexing.            (line   9)
 * -elem-indices:                         Indexing.            (line  21)
 * -every:                                Predicates.          (line  23)
 * -fifth-item:                           Other list operations.
                                                               (line 315)
 * -filter:                               Sublist selection.   (line   8)
 * -find-index:                           Indexing.            (line  32)
 * -find-indices:                         Indexing.            (line  60)
 * -find-last-index:                      Indexing.            (line  46)
 * -first:                                Other list operations.
                                                               (line 246)
 * -first-item:                           Other list operations.
                                                               (line 272)
 * -fix:                                  Other list operations.
                                                               (line 375)
 * -fixfn:                                Function combinators.
                                                               (line 224)
 * -flatten:                              List to list.        (line  34)
 * -flatten-n:                            List to list.        (line  56)
 * -flip:                                 Function combinators.
                                                               (line  95)
 * -fourth-item:                          Other list operations.
                                                               (line 305)
 * -grade-down:                           Indexing.            (line  81)
 * -grade-up:                             Indexing.            (line  71)
 * -group-by:                             Partitioning.        (line 194)
 * -if-let:                               Binding.             (line  34)
 * -if-let*:                              Binding.             (line  45)
 * -inits:                                Reductions.          (line 222)
 * -insert-at:                            List to list.        (line 110)
 * -interleave:                           Other list operations.
                                                               (line  67)
 * -interpose:                            Other list operations.
                                                               (line  57)
 * -intersection:                         Set operations.      (line  32)
 * -iota:                                 Other list operations.
                                                               (line  78)
 * -is-infix?:                            Predicates.          (line 153)
 * -is-prefix?:                           Predicates.          (line 129)
 * -is-suffix?:                           Predicates.          (line 141)
 * -iterate:                              Unfolding.           (line   9)
 * -iteratefn:                            Function combinators.
                                                               (line 201)
 * -juxt:                                 Function combinators.
                                                               (line  37)
 * -keep:                                 List to list.        (line   8)
 * -lambda:                               Binding.             (line 247)
 * -last:                                 Other list operations.
                                                               (line 262)
 * -last-item:                            Other list operations.
                                                               (line 325)
 * -let:                                  Binding.             (line  61)
 * -let*:                                 Binding.             (line 227)
 * -list:                                 Other list operations.
                                                               (line 358)
 * -map:                                  Maps.                (line  10)
 * -map-first:                            Maps.                (line  38)
 * -map-indexed:                          Maps.                (line  66)
 * -map-last:                             Maps.                (line  52)
 * -map-when:                             Maps.                (line  22)
 * -mapcat:                               Maps.                (line 128)
 * -max:                                  Reductions.          (line 286)
 * -max-by:                               Reductions.          (line 296)
 * -min:                                  Reductions.          (line 262)
 * -min-by:                               Reductions.          (line 272)
 * -non-nil:                              Sublist selection.   (line  94)
 * -none?:                                Predicates.          (line  73)
 * -not:                                  Function combinators.
                                                               (line 153)
 * -on:                                   Function combinators.
                                                               (line  75)
 * -only-some?:                           Predicates.          (line  85)
 * -orfn:                                 Function combinators.
                                                               (line 167)
 * -pad:                                  Other list operations.
                                                               (line 191)
 * -partial:                              Function combinators.
                                                               (line   8)
 * -partition:                            Partitioning.        (line  80)
 * -partition-after-item:                 Partitioning.        (line 184)
 * -partition-after-pred:                 Partitioning.        (line 151)
 * -partition-all:                        Partitioning.        (line  92)
 * -partition-all-in-steps:               Partitioning.        (line 115)
 * -partition-before-item:                Partitioning.        (line 174)
 * -partition-before-pred:                Partitioning.        (line 163)
 * -partition-by:                         Partitioning.        (line 127)
 * -partition-by-header:                  Partitioning.        (line 138)
 * -partition-in-steps:                   Partitioning.        (line 103)
 * -permutations:                         Set operations.      (line  52)
 * -powerset:                             Set operations.      (line  44)
 * -prodfn:                               Function combinators.
                                                               (line 258)
 * -product:                              Reductions.          (line 201)
 * -reduce:                               Reductions.          (line  53)
 * -reduce-from:                          Reductions.          (line   8)
 * -reduce-r:                             Reductions.          (line  72)
 * -reduce-r-from:                        Reductions.          (line  26)
 * -reductions:                           Reductions.          (line 136)
 * -reductions-from:                      Reductions.          (line 100)
 * -reductions-r:                         Reductions.          (line 154)
 * -reductions-r-from:                    Reductions.          (line 118)
 * -remove:                               Sublist selection.   (line  26)
 * -remove-at:                            List to list.        (line 146)
 * -remove-at-indices:                    List to list.        (line 159)
 * -remove-first:                         Sublist selection.   (line  43)
 * -remove-item:                          Sublist selection.   (line  83)
 * -remove-last:                          Sublist selection.   (line  64)
 * -repeat:                               Other list operations.
                                                               (line  19)
 * -replace:                              List to list.        (line  68)
 * -replace-at:                           List to list.        (line 121)
 * -replace-first:                        List to list.        (line  82)
 * -replace-last:                         List to list.        (line  96)
 * -rotate:                               Other list operations.
                                                               (line   8)
 * -rotate-args:                          Function combinators.
                                                               (line 112)
 * -rpartial:                             Function combinators.
                                                               (line  22)
 * -running-product:                      Reductions.          (line 211)
 * -running-sum:                          Reductions.          (line 190)
 * -same-items?:                          Predicates.          (line 115)
 * -second-item:                          Other list operations.
                                                               (line 285)
 * -select-by-indices:                    Sublist selection.   (line 208)
 * -select-column:                        Sublist selection.   (line 238)
 * -select-columns:                       Sublist selection.   (line 219)
 * -separate:                             Partitioning.        (line  69)
 * -setq:                                 Binding.             (line 270)
 * -slice:                                Sublist selection.   (line 104)
 * -snoc:                                 Other list operations.
                                                               (line  43)
 * -some:                                 Predicates.          (line   8)
 * -some-->:                              Threading macros.    (line  86)
 * -some->:                               Threading macros.    (line  62)
 * -some->>:                              Threading macros.    (line  74)
 * -sort:                                 Other list operations.
                                                               (line 345)
 * -splice:                               Maps.                (line  95)
 * -splice-list:                          Maps.                (line 115)
 * -split-at:                             Partitioning.        (line   8)
 * -split-on:                             Partitioning.        (line  34)
 * -split-when:                           Partitioning.        (line  52)
 * -split-with:                           Partitioning.        (line  23)
 * -sum:                                  Reductions.          (line 180)
 * -table:                                Other list operations.
                                                               (line 202)
 * -table-flat:                           Other list operations.
                                                               (line 221)
 * -tails:                                Reductions.          (line 232)
 * -take:                                 Sublist selection.   (line 120)
 * -take-last:                            Sublist selection.   (line 133)
 * -take-while:                           Sublist selection.   (line 175)
 * -third-item:                           Other list operations.
                                                               (line 295)
 * -tree-map:                             Tree operations.     (line  28)
 * -tree-map-nodes:                       Tree operations.     (line  39)
 * -tree-mapreduce:                       Tree operations.     (line  84)
 * -tree-mapreduce-from:                  Tree operations.     (line 103)
 * -tree-reduce:                          Tree operations.     (line  52)
 * -tree-reduce-from:                     Tree operations.     (line  69)
 * -tree-seq:                             Tree operations.     (line   8)
 * -unfold:                               Unfolding.           (line  25)
 * -union:                                Set operations.      (line   8)
 * -unzip:                                Other list operations.
                                                               (line 158)
 * -update-at:                            List to list.        (line 133)
 * -when-let:                             Binding.             (line   9)
 * -when-let*:                            Binding.             (line  21)
 * -zip:                                  Other list operations.
                                                               (line 107)
 * -zip-fill:                             Other list operations.
                                                               (line 150)
 * -zip-lists:                            Other list operations.
                                                               (line 131)
 * -zip-with:                             Other list operations.
                                                               (line  91)
 * dash-fontify-mode:                     Fontification of special variables.
                                                               (line   6)
 * dash-register-info-lookup:             Info symbol lookup.  (line   6)
 * global-dash-fontify-mode:              Fontification of special variables.
                                                               (line  12)
 
 
 
 Tag Table:
 Node: Top742
 Node: Installation2397
 Node: Using in a package3159
 Node: Fontification of special variables3504
 Node: Info symbol lookup4294
 Node: Functions4877
 Node: Maps6361
 Ref: -map6658
 Ref: -map-when7031
 Ref: -map-first7606
 Ref: -map-last8081
 Ref: -map-indexed8551
 Ref: -annotate9237
 Ref: -splice9724
 Ref: -splice-list10502
 Ref: -mapcat10961
 Ref: -copy11334
 Node: Sublist selection11522
 Ref: -filter11715
 Ref: -remove12262
 Ref: -remove-first12800
 Ref: -remove-last13642
 Ref: -remove-item14367
 Ref: -non-nil14767
 Ref: -slice15043
 Ref: -take15572
 Ref: -take-last15979
 Ref: -drop16410
 Ref: -drop-last16851
 Ref: -take-while17277
 Ref: -drop-while17892
 Ref: -select-by-indices18508
 Ref: -select-columns19019
 Ref: -select-column19722
 Node: List to list20185
 Ref: -keep20377
 Ref: -concat20941
 Ref: -flatten21235
 Ref: -flatten-n21991
 Ref: -replace22375
 Ref: -replace-first22836
 Ref: -replace-last23331
 Ref: -insert-at23819
 Ref: -replace-at24144
 Ref: -update-at24531
 Ref: -remove-at25019
 Ref: -remove-at-indices25504
 Node: Reductions26083
 Ref: -reduce-from26279
 Ref: -reduce-r-from27003
 Ref: -reduce28266
 Ref: -reduce-r29017
 Ref: -reductions-from30295
 Ref: -reductions-r-from31101
 Ref: -reductions31931
 Ref: -reductions-r32642
 Ref: -count33387
 Ref: -sum33611
 Ref: -running-sum33799
 Ref: -product34120
 Ref: -running-product34328
 Ref: -inits34669
 Ref: -tails34914
 Ref: -common-prefix35158
 Ref: -common-suffix35452
 Ref: -min35746
 Ref: -min-by35972
 Ref: -max36493
 Ref: -max-by36718
 Node: Unfolding37244
 Ref: -iterate37485
 Ref: -unfold37932
 Node: Predicates38737
 Ref: -some38914
 Ref: -every39331
 Ref: -any?40010
 Ref: -all?40341
 Ref: -none?41048
 Ref: -only-some?41350
 Ref: -contains?41835
 Ref: -same-items?42224
 Ref: -is-prefix?42609
 Ref: -is-suffix?42935
 Ref: -is-infix?43261
 Ref: -cons-pair?43615
 Node: Partitioning43940
 Ref: -split-at44128
 Ref: -split-with44792
 Ref: -split-on45192
 Ref: -split-when45863
 Ref: -separate46500
 Ref: -partition46939
 Ref: -partition-all47388
 Ref: -partition-in-steps47813
 Ref: -partition-all-in-steps48307
 Ref: -partition-by48789
 Ref: -partition-by-header49167
 Ref: -partition-after-pred49768
 Ref: -partition-before-pred50215
 Ref: -partition-before-item50600
 Ref: -partition-after-item50907
 Ref: -group-by51209
 Node: Indexing51642
 Ref: -elem-index51844
 Ref: -elem-indices52239
 Ref: -find-index52619
 Ref: -find-last-index53108
 Ref: -find-indices53612
 Ref: -grade-up54017
 Ref: -grade-down54424
 Node: Set operations54838
 Ref: -union55021
 Ref: -difference55459
 Ref: -intersection55871
 Ref: -powerset56303
 Ref: -permutations56513
 Ref: -distinct56809
 Node: Other list operations57183
 Ref: -rotate57408
 Ref: -repeat57761
 Ref: -cons*58040
 Ref: -snoc58456
 Ref: -interpose58866
 Ref: -interleave59160
 Ref: -iota59526
 Ref: -zip-with60009
 Ref: -zip60723
 Ref: -zip-lists61552
 Ref: -zip-fill62250
 Ref: -unzip62572
 Ref: -cycle63314
 Ref: -pad63713
 Ref: -table64032
 Ref: -table-flat64818
 Ref: -first65823
 Ref: -last66309
 Ref: -first-item66643
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