parens.texi (30510B)
1 @node Between the parens, Cheat sheet, The REPL, Top 2 @chapter Between the parens 3 4 A good REPL is a must, but just about half the story of a good Scheme 5 hacking environment. Well, perhaps a bit more than a half; but, at any 6 rate, one surely needs also a pleasant way of editing source code. Don't 7 pay attention to naysayers: Emacs comes with an excellent editor 8 included for about any language on Earth, and just the best one when 9 that language is sexpy (especially if you use 10 @ifhtml 11 @ref{paredit,,Paredit}). 12 @end ifhtml 13 @ifnothtml 14 Paredit). 15 @end ifnothtml 16 Geiser's support for writing Scheme code adds to Emacs' 17 @code{scheme-mode}, rather than supplanting it; and it does so by means 18 of a minor mode (unimaginatively dubbed @code{geiser-mode}) that defines 19 a bunch of new commands to try and, with the help of the same Scheme 20 process giving you the REPL, make those Scheme buffers come to life. 21 22 @menu 23 * Activating Geiser:: 24 * The source and the REPL:: 25 * Documentation helpers:: 26 * To eval or not to eval:: 27 * To err perchance to debug:: 28 * Jumping around:: 29 * Geiser writes for you:: 30 @end menu 31 32 @node Activating Geiser, The source and the REPL, Between the parens, Between the parens 33 @section Activating Geiser 34 35 @cindex geiser-mode 36 @img{geiser-mode, right} 37 With Geiser installed following any of the 38 procedures described in @ref{The quick and easy way} or @ref{From the 39 source's mouth}, Emacs will automatically activate @i{geiser-mode} when 40 opening a Scheme buffer. Geiser also instructs Emacs to consider files 41 with the extension @file{rkt} part of the family, so that, in principle, 42 there's nothing you need to do to ensure that Geiser's extensions will 43 be available, out of the box, when you start editing Scheme code. 44 45 Indications that everything is working according to plan include the 46 'Geiser' minor mode indicator in your mode-line and the appearance of a 47 new entry for Geiser in the menu bar. If, moreover, the mode-line 48 indicator is the name of a Scheme implementation, you're indeed in a 49 perfect world; otherwise, don't despair and keep on reading: i'll tell 50 you how to fix that in a moment. 51 52 @cindex geiser-mode commands 53 The menu provides a good synopsis of everything Geiser brings to the 54 party, including those keyboard shortcuts we Emacsers love. If you're 55 seeing the name of your favourite Scheme implementation in the 56 mode-line, have a running REPL and are comfortable with Emacs, you can 57 stop reading now and, instead, discover Geiser's joys by yourself. I've 58 tried to make Geiser as self-documenting as any self-respecting Emacs 59 package should be. If you follow this route, make sure to take a look at 60 Geiser's customization buffers (@kbd{M-x customize-group @key{RET} 61 geiser}): there's lot of fine-tuning available there. You might also 62 want to take a glance at 63 @ifhtml 64 our @ref{Cheat sheet,,cheat sheet}. 65 @end ifhtml 66 @ifnothtml 67 the tables in @pxref{Cheat sheet, our cheat sheet}. 68 @end ifnothtml 69 70 Since @i{geiser-mode} is a minor mode, you can toggle it with 71 @kbd{M-x geiser-mode}, and control its activation in hooks with the 72 functions @code{turn-on-geiser-mode} and @code{turn-off-geiser-mode}. 73 If, for some reason i cannot fathom, you prefer @i{geiser-mode} not 74 to be active by default, customizing @code{geiser-mode-auto-p} to 75 @code{nil} will do the trick. 76 77 @cindex scheme file extensions 78 And if you happen to use a funky extension for your Scheme files that is 79 not recognised as such by Emacs, just tell her about it with: 80 81 @example 82 (add-to-list 'auto-mode-alist '("\\.funky-extension\\'" . scheme-mode)) 83 @end example 84 85 @cindex useless wretch 86 Now, @i{geiser-mode} is just a useless wretch unless there's a running 87 Scheme process backing it up. Meaning that virtually all the commands it 88 provides require a REPL up and running, preferably corresponding to 89 the correct Scheme implementation. In the following section, we'll see 90 how to make sure that that's actually the case. 91 92 @node The source and the REPL, Documentation helpers, Activating Geiser, Between the parens 93 @section The source and the REPL 94 95 As i've already mentioned a couple of times, @i{geiser-mode} needs a 96 running REPL to be operative. Thus, a common usage pattern will be 97 for you to first call @code{geiser} 98 @ifhtml 99 (or @ref{choosing-impl,,one of its variants}), 100 @end ifhtml 101 @ifnothtml 102 (or one of its variants, e.g. @code{run-guile}), 103 @end ifnothtml 104 and then open some Scheme files; 105 but there's nothing wrong in first opening a couple Scheme buffers and 106 then starting the REPL (you can even find it more convenient, since 107 pressing @kbd{C-c C-z} in a Scheme buffer will start the REPL for 108 you). Since Geiser supports more than one Scheme implementation, though, 109 there's the problem of knowing which of them is to be associated with 110 each Scheme source file. Serviceable as it is, @i{geiser-mode} will try 111 to guess the correct implementation for you, according to the algorithm 112 described below. 113 @ifhtml 114 If you find that Geiser is already guessing right the Scheme 115 implementation, feel free to skip to the @ref{switching-repl-buff,,next 116 subsection}. 117 @end ifhtml 118 119 @subsubheading How Geiser associates a REPL to your Scheme buffer 120 @cindex scheme implementation, choosing 121 @anchor{repl-association} To determine what Scheme implementation 122 corresponds to a given source file, Geiser uses the following algorithm: 123 124 @enumerate 125 @item 126 If the file-local variable @code{geiser-scheme-implementation} is 127 defined, its value is used. A common way of setting buffer-local 128 variables is to put them in a comment near the beginning of the file, 129 surrounded by @code{-*-} marks, as in: 130 131 @example 132 ;; -*- geiser-scheme-implementation: guile -*- 133 @end example 134 135 @item 136 If you've customized @code{geiser-active-implementations} so that it's a 137 single-element 138 @ifhtml 139 list (as explained in @ref{choosing-impl,,here}), 140 @end ifhtml 141 @ifnothtml 142 list, 143 @end ifnothtml 144 that element is used as the chosen implementation. 145 @item 146 The contents of the file is scanned for hints on its associated 147 implementation. For instance, files that contain a @code{#lang} 148 directive will be considered Racket source code, while those with a 149 @code{define-module} form in them will be assigned to a Guile REPL. 150 @item 151 The current buffer's file name is checked against the rules given in 152 @code{geiser-implementations-alist}, and the first match is applied. You 153 can provide your own rules by customizing this variable, as explained 154 below. 155 @item 156 If we haven't been lucky this far and you have customized 157 @code{geiser-default-implementation} to the name of a supported 158 implementation, we'll follow your lead. 159 @item 160 See? That's the problem of being a smart aleck: one's always outsmarted 161 by people around. At this point, @i{geiser-mode} will humbly give up and 162 ask you to explicitly choose the Scheme implementation. 163 @end enumerate 164 165 As you can see in the list above, there are several ways to influence 166 Geiser's guessing by means of customizable variables. The most direct (and 167 most impoverishing) is probably limiting the active implementations to a 168 single one, while customizing @code{geiser-implementations-alist} is the 169 most flexible (and, unsurprisingly, also the most complex). Here's the 170 default value for the latter variable: 171 172 @example 173 (((regexp "\\.scm$") guile) 174 ((regexp "\\.ss$") racket) 175 ((regexp "\\.rkt$") racket)) 176 @end example 177 178 @noindent 179 which describes the simple heuristic that files with @file{.scm} as 180 extension are by default associated to a Guile REPL while those ending 181 in @file{.ss} or @file{.rkt} correspond to Racket's implementation (with 182 the caveat that these rules are applied only if the previous heuristics 183 have failed to detect the correct implementation, and that they'll match 184 only if the corresponding implementation is active). You can add rules 185 to @code{geiser-implementations-alist} (or replace all of them) by 186 customizing it. Besides regular expressions, you can also use a 187 directory name; for instance, the following snippet: 188 189 @example 190 (eval-after-load "geiser-impl" 191 '(add-to-list 'geiser-implementations-alist 192 '((dir "/home/jao/prj/frob") guile))) 193 @end example 194 195 @noindent 196 will add a new rule that says that any file inside my 197 @file{/home/jao/prj/frob} directory (or, recursively, any of its 198 children) is to be assigned to Guile. Since rules are first matched, 199 first served, this new rule will take precedence over the default ones. 200 201 @cindex autostart REPL 202 @cindex start REPL, automatically 203 A final tip: if you want Geiser to start automatically a REPL for you if 204 it notices that there's no one active when it enters @i{geiser-mode}, 205 you can customize @code{geiser-mode-start-repl-p} to @code{t}. 206 207 @subsubheading Managing multiple scheme projects 208 @cindex dir-locals 209 @cindex project.el 210 @cindex projectile 211 @cindex projects 212 @anchor{repl-per-project} By default, Geiser will re-use a single REPL 213 for all buffers sharing the same scheme implementation. This works well 214 enough in many cases, but may become problematic (or at least annoying) 215 when working on multiple projects with separate dependencies and include 216 paths. 217 218 @cindex geiser-repl-per-project-p 219 Geiser provides optional support for using separate REPLs for each 220 project, which can be enabled by customizing 221 @code{geiser-repl-current-project-function} and selecting your Emacs 222 project-management library of choice (eg. @code{project.el} or 223 @code{projectile}). With this configured, if you want new REPLs to 224 automatically associate themselves with the current project, so that all 225 Geiser commands will ignore REPLs that are not associated with the 226 project, customize the toggle @code{geiser-repl-per-project-p} to 227 @code{t} and you're all set up. 228 229 @cindex geiser-repl-add-project-path-p 230 This can be very convenient when used with a @file{.dir-locals.el} in 231 the project root to set include paths, ensuring that Geiser REPLs will 232 always know where to find your project's modules or dependencies. 233 Geiser automatically handles the common case of the project root 234 belonging to the load path: unless you tell it otherwise (using the 235 customisable flag @code{geiser-repl-add-project-path-p}, which defaults 236 to @code{t}), it will add the result of calling 237 @code{geiser-repl-current-project-function} to the REPLs load path on 238 startup. 239 240 @subsubheading Switching between source files and the REPL 241 @cindex switching to REPL 242 @cindex switching to source 243 @anchor{switching-repl-buff} Once you have a working @i{geiser-mode}, 244 you can switch from Scheme source buffers to the REPL or @kbd{C-c 245 C-z}. Those shortcuts map to the interactive command 246 @code{geiser-repl-switch}. 247 248 @cindex switching to module 249 If you use a numeric prefix, as in @kbd{C-u C-c C-z}, besides being 250 teleported to the REPL, the latter will switch to the namespace of the 251 Scheme source file, as if you had used @kbd{C-c C-m} in the REPL, with 252 the source file's module as argument; 253 cf. discussion in 254 @altr{Switching context,,Switching context,. This} 255 command is also bound to @kbd{C-c C-a}. 256 257 Once you're in the REPL, the same @kbd{C-c C-z} shortcut will bring 258 you back to the buffer you jumped from, provided you don't kill the 259 Scheme process in between. This is why the command is called 260 @i{geiser-repl-switch} instead of @i{switch-to-repl}, and what makes it 261 really handy, if you ask me. 262 263 @cindex switching schemes 264 If for some reason you're not happy with the Scheme implementation that 265 Geiser has assigned to your file, you can change it with @kbd{C-c C-s}, 266 and you probably should take a look at 267 @ifhtml 268 @ref{repl-association,,the previous subsection} 269 @end ifhtml 270 @ifnothtml 271 the previous subsection 272 @end ifnothtml 273 to make sure that Geiser 274 doesn't get confused again. 275 276 @subsubheading A note about context 277 As explained before (@pxref{Modus operandi}), all Geiser activities take 278 place in the context of the @i{current namespace}, which, for Scheme 279 buffers, corresponds to the module that the Scheme implementation 280 associates to the source file at hand (for instance, in Racket, there's 281 a one-to-one correspondence between paths and modules, while Guile 282 relies on explicit @code{define-module} forms in the source file). 283 284 Now that we have @code{geiser-mode} happily alive in our Scheme buffers 285 and communicating with the right REPL instance, let us see what it 286 can do for us, besides jumping to and fro. 287 288 @node Documentation helpers, To eval or not to eval, The source and the REPL, Between the parens 289 @section Documentation helpers 290 291 @subsubheading Autodoc redux 292 293 @cindex autodoc, in scheme buffers 294 The first thing you will notice by moving around Scheme source is that, 295 every now and then, the echo area lights up with the same autodoc 296 messages we know and love from our REPL forays. This happens every 297 time the Scheme process is able to recognise an identifier in the 298 buffer, and provide information either on its value (for variables) or 299 on its arity and the name of its formal arguments (for procedures and 300 macros). That information will only be available if the module the 301 identifier belongs to has been loaded in the running Scheme image. So it 302 can be the case that, at first, no autodoc is shown for identifiers 303 defined in the file you're editing. But as soon as you evaluate them 304 (either individually or collectively using any of the devices described 305 in @ref{To eval or not to eval}) their signatures will start appearing 306 in the echo area. 307 308 @cindex disabling autodoc 309 @cindex manual autodoc 310 Autodoc activation is controlled by a minor mode, @code{geiser-autodoc}, 311 which you can toggle with @kbd{M-x geiser-autodoc-mode}, or its associated 312 keyboard shortcut, @kbd{C-c C-d a}. That @t{/A} indicator in the 313 mode-line is telling you that autodoc is active. If you prefer that it 314 be inactive by default (e.g., because you're connecting to a really 315 remote scheme and want to minimize network exchanges), just set 316 @code{geiser-mode-autodoc-p} to @code{nil} in your customization files. 317 Even when autodoc mode is off, you can use @code{geiser-autodoc-show}, 318 bound by default to @kbd{C-c C-d s}, to show the autodoc string for the 319 symbol at point. 320 321 @cindex autodoc explained 322 @img{autodoc-scm, right} 323 The way autodoc displays information deserves 324 some explanation. It will first show the name of the module where the 325 identifier at hand is defined, followed by a colon and the identifier 326 itself. If the latter corresponds to a procedure or macro, it will be 327 followed by a list of argument names, starting with the ones that are 328 required. Then there comes a list of optional arguments, if any, 329 enclosed in parentheses. When an optional argument has a default value 330 (or a form defining its default value), autodoc will display it after 331 the argument name. When the optional arguments are keywords, their names 332 are prefixed with ``#:'' (i.e., their names @i{are} keywords). An 333 ellipsis (@dots{}) serves as a marker of an indeterminate number of 334 parameters, as is the case with @i{rest} arguments or when autodoc 335 cannot fathom the exact number of arguments (this is often the case with 336 macros defined using @code{syntax-case}). Another way in which autodoc 337 displays its ignorance is by using an underscore to display parameters 338 whose name is beyond its powers. 339 340 @img{autodoc-multi, right} 341 It can also be the case that a function or 342 macro has more than one signature (e.g., functions defined using 343 @code{case-lambda}, or some @code{syntax-rules} macros, for which Geiser 344 has often the black magic necessary to retrieve their actual arities). 345 In those cases, autodoc shows all known signatures (using the above 346 rules for each one) separated by a vertical bar (|). 347 348 As you have already noticed, the whole autodoc message is enclosed in 349 parentheses. After all, we're talking about Scheme here. 350 351 @cindex autodoc for variables 352 @img{autodoc-var, right} 353 Finally, life is much easier when your cursor 354 is on a symbol corresponding to a plain variable: you'll see in the echo 355 area its name, preceded by the module where it's defined, and followed 356 by its value, with an intervening arrow for greater effect. This time, 357 there are no enclosing parentheses (i hope you see the logic in my 358 madness). 359 360 @cindex autodoc customized 361 You can change the way Geiser displays the module/identifier combo by 362 customizing @code{geiser-autodoc-identifier-format}. For example, if you 363 wanted a tilde surrounded by spaces instead of a colon as a separator, 364 you would write something like: 365 366 @example 367 (setq geiser-autodoc-identifier-format "%s ~ %s") 368 @end example 369 370 @noindent 371 in your Emacs initialisation files. There's also a face 372 (@code{geiser-font-lock-autodoc-identifier}) that you can customize (for 373 instance, with @kbd{M-x customize-face}) to change the appearance of the 374 text. And another one (@code{geiser-font-lock-autodoc-current-arg}) that 375 controls how the current argument position is highlighted. 376 377 @subsubheading Other documentation commands 378 379 @anchor{doc-browser}Sometimes, autodoc won't provide enough information 380 for you to understand what a function does. In those cases, you can ask 381 Geiser to ask the running Scheme for further information on a given 382 identifier or module. 383 384 @cindex documentation for symbol 385 @cindex docstrings, maybe 386 For symbols, the incantation is @kbd{M-x geiser-doc-symbol-at-point}, or 387 @kbd{C-c C-d C-d} for short. If the associated Scheme supports 388 docstrings (as, for instance, Guile does), you'll be teleported to a new 389 Emacs buffer displaying Geiser's documentation browser, filled with 390 information about the identifier, including its docstring (if any; 391 unfortunately, that an implementation supports docstrings doesn't mean 392 that they're used everywhere). 393 394 @imgc{docstring} 395 396 Pressing @kbd{q} in the documentation buffer will bring you back, 397 enlightened, to where you were. There's also a handful of other 398 navigation commands available in that buffer, which you can discover by 399 means of its menu or via the good old @kbd{C-h m} command. And feel free 400 to use the navigation buttons and hyperlinks that justify my calling 401 this buffer a documentation browser. 402 403 For Racket, which does not support docstrings out of the box, this 404 command will provide less information, but the documentation browser 405 will display the corresponding contract when it's available, as well as 406 some other tidbits for re-exported identifiers. 407 408 @imgc{docstring-racket} 409 410 You can also ask Geiser to display information about a module, in the 411 form of a list of its exported identifiers, using @kbd{C-c C-d C-m}, 412 exactly as you would do in 413 @altr{repl-mod,the REPL,The REPL,.} 414 415 In both cases, the documentation browser will show a couple of buttons 416 giving you access to further documentation. First, you'll see a button 417 named @i{source}: pressing it you'll jump to the symbol's definition. 418 The second button, dubbed @i{manual}, will open the Scheme 419 implementation's manual page for the symbol at hand. For Racket, that 420 will open your web browser displaying the corresponding reference's page 421 (using the HTML browser in Racket's configuration, which you can edit in 422 DrRacket's preferences dialog, or by setting 423 @code{plt:framework-pref:external-browser} directly in 424 @file{~/.racket/racket-prefs.rktd}), while in Guile a lookup will be 425 performed in the texinfo manual. 426 427 @cindex Guile info nodes 428 For Guile, the manual lookup uses the info indexes in the standard 429 Guile info nodes, which are usually named ``guile'' or ``guile-2.0''. 430 If yours are named differently, just add your name to the customizable 431 variable @code{geiser-guile-manual-lookup-nodes}. 432 433 A list of all navigation commands in the documentation browser is 434 available in 435 @altr{Documentation browser,our cheat-sheet,Documentation browser,.} 436 437 @cindex opening manual pages 438 You can also skip the documentation browser and jump directly to the 439 manual page for the symbol at point with the command 440 @code{geiser-doc-look-up-manual}, bound to @kbd{C-c C-d i}. 441 442 @node To eval or not to eval, To err perchance to debug, Documentation helpers, Between the parens 443 @section To eval or not to eval 444 445 @cindex philosophy 446 @cindex incremental development 447 One of Geiser's main goals is to facilitate incremental development. 448 You might have noticed that i've made a big fuss of Geiser's ability to 449 recognize context, by dint of being aware of the namespace where its 450 operations happen. 451 452 That awareness is especially important when evaluating code in your 453 scheme buffers, using the commands described below. They allow you to 454 send code to the running Scheme with a granularity ranging from whole 455 files to single s-expressions. That code will be evaluated in the module 456 associated with the file you're editing, allowing you to redefine values 457 and procedures to your heart's (and other modules') content. 458 459 @cindex incremental development, evil 460 Macros are, of course, another kettle of fish: one needs to re-evaluate 461 uses of a macro after redefining it. That's not a limitation imposed by 462 Geiser, but a consequence of how macros work in Scheme (and other 463 Lisps). There's also the risk that you lose track of what's actually 464 defined and what's not during a given session. But, 465 @uref{https://jaortega.wordpress.com/2009/03/29/from-my-cold-prying-hands, 466 in my opinion}, those are limitations we lispers are aware of, and they 467 don't force us to throw the baby with the bathwater and ditch 468 incremental evaluation. Some people disagree; if you happen to find 469 @uref{https://blog.racket-lang.org/2009/03/the-drscheme-repl-isnt-the-one-in-emacs.html, 470 their arguments} convincing, you don't have to throw away Geiser 471 together with the baby: @kbd{M-x geiser-restart-repl} will let you 472 restart the REPL as many times as you see fit. Moreover, you can invoke 473 @kbd{geiser-compile-current-buffer} and @kbd{geiser-load-current-buffer} 474 with a prefix argument (that'd be something like @kbd{C-u C-c C-k} for 475 compilation, for instance), to tell Geiser to restart the REPL 476 associated with a buffer before compiling or loading its current 477 contents. 478 479 @cindex evaluation 480 @cindex incremental development, not evil 481 For all of you auld bearded lispers still with me, here are some of the 482 commands performing incremental evaluation in Geiser. 483 484 @code{geiser-eval-last-sexp}, bound to @kbd{C-x C-e}, will eval the 485 s-expression just before point. If you use a prefix, as in @kbd{C-u C-x 486 C-e}, besides evaluating it the expression is inserted in the the 487 buffer. 488 489 @code{geiser-eval-definition}, bound to @kbd{C-M-x}, finds the topmost 490 definition containing point and sends it for evaluation. The variant 491 @code{geiser-eval-definition-and-go} (@kbd{C-c M-e}) works in the same 492 way, but it also teleports you to REPL after the evaluation. 493 494 @code{geiser-eval-region}, bound to @kbd{C-c C-r}, evals the current 495 region. Again, there's an @i{and-go} version available, 496 @code{geiser-eval-region-and-go}, bound to @kbd{C-c M-r}. And, if you 497 want to extend the evaluated region to the whole buffer, there is 498 @code{geiser-eval-buffer}, bound to @kbd{C-c C-b} and its companion 499 @code{geiser-eval-buffer-and-go}, bound to @kbd{C-c M-b}. 500 501 @cindex evaluating images 502 @cindex image display 503 For all the commands above, the result of the evaluation is displayed in 504 the minibuffer, unless it causes a (Scheme-side) error (@pxref{To err 505 perchance to debug}), or, for schemes supporting them (such as Racket), 506 the evaluation yields an image, in which case you'll see it in popping 507 up in the Geiser debug buffer (if your Emacs runs under the auspices of 508 a graphical toolkit), or via an external viewer if you set 509 @code{geiser-image-viewer} to the path of an appropriate visualization 510 program (see also @ref{Seeing is believing} for more on image support). 511 512 At the risk of repeating myself, i'll remind you that all these 513 evaluations will take place in the namespace of the module corresponding 514 to the Scheme file from which you're sending your code, which, in 515 general, will be different from the REPL's current module. And, if all 516 goes according to plan, (re)defined variables and procedures should be 517 immediately visible inside and, if exported, outside their module. 518 519 Besides evaluating expressions, definitions and regions, you can also 520 macro-expand them. The corresponding key bindings start with the prefix 521 @kbd{C-c C-m} and end, respectively, with @kbd{C-e}, @kbd{C-x} and 522 @kbd{C-r}. The result of the macro expansion always appears in a pop up 523 buffer. 524 525 @cindex interrupt evaluation 526 All the evaluations and expansions performed by the commands above are 527 asynchronous@footnote{For local REPLs, where we can easily send an 528 interrupt signal to the scheme process; remote REPLs are another kettle 529 of fish in this regard, and generally interruptions are supported: 530 you'll just have to kill the connection if caught in a loop.}, so that 531 you can move around while the answer is being computed. The command 532 @code{geiser-eval-interrupt}, bound to @kbd{C-c C-i} will interrupt any 533 on-going evaluation and, when the scheme implementation supports a 534 debugger, bring you to a buffer where you can perform buffer actions in 535 the interrupted evaluation's context. 536 537 Oh, didn't i mention we have support for debuggers? Let's talk about 538 that next. 539 540 @node To err perchance to debug, Jumping around, To eval or not to eval, Between the parens 541 @section To err: perchance to debug 542 543 @cindex to err is schemey 544 @cindex backtraces 545 When an error occurs during evaluation, it will be reported according to 546 the capabilities of the underlying Scheme REPL. 547 548 @cindex error buffer 549 In most schemes, you'll be presented with a backtrace, in a new buffer 550 where file paths locating the origin of the error are click-able (you 551 can navigate them using the @key{TAB} key, and use @key{RET} or the 552 mouse to jump to the offending spot; or invoke Emacs' stock commands 553 @code{next-error} and @code{previous-error}, bound to @kbd{M-g n} and 554 @kbd{M-g p} by default). 555 556 @imgc{eval-error} 557 558 By default, Geiser will tele-transport your pointer to the debug buffer: 559 if you prefer to stay in the source buffer, set 560 @code{geiser-debug-jump-to-debug} to nil. 561 562 For schemes with good debug support (Guile is one), the debug buffers 563 offer a @i{debugging menu}, accesible via the @code{,} (that's a comma) 564 key. If you press it, a transient menu will appear, offering you a 565 variety of actions, including showing local variable values or a more 566 detailed backtrace or frame display. This is the same interface you'll 567 encounter the in case of interrupted evaluations, either by your 568 explicit @kbd{C-c C-i} command or because a breakpoint has been 569 previosuly set. 570 571 In addition, Geiser will sometimes report warnings for otherwise 572 successful evaluations. In those cases, it won't enter the debugger, 573 just report the warnings in a debug buffer. 574 575 @node Jumping around, Geiser writes for you, To err perchance to debug, Between the parens 576 @section Jumping around 577 578 @cindex jumping in scheme buffers 579 This one feature is as sweet as it is easy to explain: @kbd{M-.} 580 (@code{geiser-edit-symbol-at-point}) will open the file where the 581 identifier around point is defined and land your point on its 582 definition. To return to where you were, press @kbd{M-,} 583 (@code{geiser-pop-symbol-stack}). This command works also for module 584 names: Geiser first tries to locate a definition for the identifier at 585 point and, if that fails, a module with that name; if the latter 586 succeeds, the file where the module is defined will pop up. 587 588 Sometimes, the underlying Scheme will tell Geiser only the file where 589 the symbol is defined, but Geiser will use some heuristics (read, 590 regular expressions) to locate the exact line and bring you there. Thus, 591 if you find Geiser systematically missing your definitions, send a 592 message to the @email{geiser-users@@nongnu.org, mailing list}, and we'll 593 try to make the algorithm smarter. 594 595 @cindex jumping customized 596 You can control how the destination buffer pops up by setting 597 @code{geiser-edit-symbol-method} to either @code{nil} (to open the file 598 in the current window), @code{'window} (other window in the same frame) 599 or @code{'frame} (in a new frame). 600 601 @node Geiser writes for you, , Jumping around, Between the parens 602 @section Geiser writes for you 603 604 @cindex completion in scheme buffers 605 No self-respecting programming mode would be complete without 606 completion. In geiser-mode, identifier completion is bound to 607 @kbd{M-@key{TAB}}, and will offer all visible identifiers starting with 608 the prefix before point. Visible here means all symbols imported or 609 defined in the current namespace plus locally bound ones. E.g., if 610 you're at the end of the following partial expression: 611 612 @example 613 (let ((default 42)) 614 (frob def 615 @end example 616 617 @noindent 618 and press @kbd{M-@key{TAB}}, one of the possible completions will be 619 @code{default}. 620 621 @cindex partial completion 622 After obtaining the list of completions from the running Scheme, Geiser 623 uses the standard Emacs completion machinery to display them. That 624 means, among other things, that partial completion is available: just 625 try to complete @code{d-s} or @code{w-o-t-s} to see why this is a good 626 thing. Partial completion won't work if you have disabled it globally in 627 your Emacs configuration: if you don't know what i'm talking about, 628 never mind: Geiser's partial completion will work for you out of the 629 box. 630 631 @cindex smart tabs 632 If you find the @kbd{M} modifier annoying, you always have the option to 633 activate @code{geiser-smart-tab-mode}, which will make the @key{TAB} key 634 double duty as the regular Emacs indentation command (when the cursor is 635 not near a symbol) and Geiser's completion function. If you want this 636 smarty pants mode always on in Scheme buffers, customize 637 @code{geiser-mode-smart-tab-p} to @code{t}. 638 639 @cindex completion for module names 640 Geiser also knows how to complete module names: if no completion for the 641 prefix at point is found among the currently visible bindings, it will 642 try to find a module name that matches it. You can also request 643 explicitly completion only over module names using @kbd{M-`} (that's a 644 backtick). 645 646 Besides completion, there's also this little command, 647 @code{geiser-squarify}, which will toggle the delimiters of the 648 innermost list around point between round and square brackets. It is 649 bound to @kbd{C-c C-e [}. With a numeric prefix (as in, say, @kbd{M-2 650 C-c C-e [}), it will perform that many toggles, forward for positive 651 values and backward for negative ones. 652 653 @subheading Caveat about completion 654 655 It is possible for Geiser to hang your Emacs process when trying to 656 complete symbols. This can happen in the REPL itself or even in a 657 Scheme buffer that is attached to the REPL process. For more details 658 on how to fix this problem, @ref{completion-caveat,,Caveat about 659 completion & the REPL} 660 661 @c Local Variables: 662 @c mode: texinfo 663 @c TeX-master: "geiser" 664 @c End: