code.delx.au - gnu-emacs/blob - lisp/ielm.el

   1 ;;; ielm.el --- interaction mode for Emacs Lisp
   2
   3 ;; Copyright (C) 1994, 2001, 2002, 2003, 2004, 2005,
   4 ;;   2006, 2007, 2008, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
   5
   6 ;; Author: David Smith <maa036@lancaster.ac.uk>
   7 ;; Maintainer: FSF
   8 ;; Created: 25 Feb 1994
   9 ;; Keywords: lisp
  10
  11 ;; This file is part of GNU Emacs.
  12
  13 ;; GNU Emacs is free software: you can redistribute it and/or modify
  14 ;; it under the terms of the GNU General Public License as published by
  15 ;; the Free Software Foundation, either version 3 of the License, or
  16 ;; (at your option) any later version.
  17
  18 ;; GNU Emacs is distributed in the hope that it will be useful,
  19 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ;; GNU General Public License for more details.
  22
  23 ;; You should have received a copy of the GNU General Public License
  24 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  25
  26 ;;; Commentary:
  27
  28 ;; Provides a nice interface to evaluating Emacs Lisp expressions.
  29 ;; Input is handled by the comint package, and output is passed
  30 ;; through the pretty-printer.
  31
  32 ;; To start: M-x ielm.  Type C-h m in the *ielm* buffer for more info.
  33
  34 ;;; Code:
  35
  36 (require 'comint)
  37 (require 'pp)
  38
  39 ;;; User variables
  40
  41 (defgroup ielm nil
  42   "Interaction mode for Emacs Lisp."
  43   :group 'lisp)
  44
  45
  46 (defcustom ielm-noisy t
  47   "If non-nil, IELM will beep on error."
  48   :type 'boolean
  49   :group 'ielm)
  50
  51 (defcustom ielm-prompt-read-only t
  52   "If non-nil, the IELM prompt is read only.
  53 The read only region includes the newline before the prompt.
  54 Setting this variable does not affect existing IELM runs.
  55 This works by setting the buffer-local value of `comint-prompt-read-only'.
  56 Setting that value directly affects new prompts in the current buffer.
  57
  58 If this option is enabled, then the safe way to temporarily
  59 override the read-only-ness of IELM prompts is to call
  60 `comint-kill-whole-line' or `comint-kill-region' with no
  61 narrowing in effect.  This way you will be certain that none of
  62 the remaining prompts will be accidentally messed up.  You may
  63 wish to put something like the following in your `.emacs' file:
  64
  65 \(add-hook 'ielm-mode-hook
  66           '(lambda ()
  67              (define-key ielm-map \"\\C-w\" 'comint-kill-region)
  68              (define-key ielm-map [C-S-backspace]
  69                'comint-kill-whole-line)))
  70
  71 If you set `comint-prompt-read-only' to t, you might wish to use
  72 `comint-mode-hook' and `comint-mode-map' instead of
  73 `ielm-mode-hook' and `ielm-map'.  That will affect all comint
  74 buffers, including IELM buffers.  If you sometimes use IELM on
  75 text-only terminals or with `emacs -nw', you might wish to use
  76 another binding for `comint-kill-whole-line'."
  77   :type 'boolean
  78   :group 'ielm
  79   :version "22.1")
  80
  81 (defcustom ielm-prompt "ELISP> "
  82   "Prompt used in IELM.
  83 Setting this variable does not affect existing IELM runs.
  84
  85 Interrupting the IELM process with \\<ielm-map>\\[comint-interrupt-subjob],
  86 and then restarting it using \\[ielm], makes the then current
  87 default value affect _new_ prompts.  Unless the new prompt
  88 differs only in text properties from the old one, IELM will no
  89 longer recognize the old prompts.  However, executing \\[ielm]
  90 does not update the prompt of an *ielm* buffer with a running process.
  91 For IELM buffers that are not called `*ielm*', you can execute
  92 \\[inferior-emacs-lisp-mode] in that IELM buffer to update the value,
  93 for new prompts.  This works even if the buffer has a running process."
  94   :type 'string
  95   :group 'ielm)
  96
  97 (defvar ielm-prompt-internal "ELISP> "
  98   "Stored value of `ielm-prompt' in the current IELM buffer.
  99 This is an internal variable used by IELM.  Its purpose is to
 100 prevent a running IELM process from being messed up when the user
 101 customizes `ielm-prompt'.")
 102
 103 (defcustom ielm-dynamic-return t
 104   "Controls whether \\<ielm-map>\\[ielm-return] has intelligent behavior in IELM.
 105 If non-nil, \\[ielm-return] evaluates input for complete sexps, or inserts a newline
 106 and indents for incomplete sexps.  If nil, always inserts newlines."
 107   :type 'boolean
 108   :group 'ielm)
 109
 110 (defcustom ielm-dynamic-multiline-inputs t
 111   "Force multiline inputs to start from column zero?
 112 If non-nil, after entering the first line of an incomplete sexp, a newline
 113 will be inserted after the prompt, moving the input to the next line.
 114 This gives more frame width for large indented sexps, and allows functions
 115 such as `edebug-defun' to work with such inputs."
 116   :type 'boolean
 117   :group 'ielm)
 118
 119 (defcustom ielm-mode-hook nil
 120   "Hooks to be run when IELM (`inferior-emacs-lisp-mode') is started."
 121   :options '(turn-on-eldoc-mode)
 122   :type 'hook
 123   :group 'ielm)
 124 (defvaralias 'inferior-emacs-lisp-mode-hook 'ielm-mode-hook)
 125
 126 (defvar * nil
 127   "Most recent value evaluated in IELM.")
 128
 129 (defvar ** nil
 130   "Second-most-recent value evaluated in IELM.")
 131
 132 (defvar *** nil
 133   "Third-most-recent value evaluated in IELM.")
 134
 135 (defvar ielm-match-data nil
 136   "Match data saved at the end of last command.")
 137
 138 (defvar *1 nil
 139   "During IELM evaluation, most recent value evaluated in IELM.
 140 Normally identical to `*'.  However, if the working buffer is an IELM
 141 buffer, distinct from the process buffer, then `*' gives the value in
 142 the working buffer, `*1' the value in the process buffer.
 143 The intended value is only accessible during IELM evaluation.")
 144
 145 (defvar *2 nil
 146   "During IELM evaluation, second-most-recent value evaluated in IELM.
 147 Normally identical to `**'.  However, if the working buffer is an IELM
 148 buffer, distinct from the process buffer, then `**' gives the value in
 149 the working buffer, `*2' the value in the process buffer.
 150 The intended value is only accessible during IELM evaluation.")
 151
 152 (defvar *3 nil
 153   "During IELM evaluation, third-most-recent value evaluated in IELM.
 154 Normally identical to `***'.  However, if the working buffer is an IELM
 155 buffer, distinct from the process buffer, then `***' gives the value in
 156 the working buffer, `*3' the value in the process buffer.
 157 The intended value is only accessible during IELM evaluation.")
 158
 159 ;;; System variables
 160
 161 (defvar ielm-working-buffer nil
 162   "Buffer in which IELM sexps will be evaluated.
 163 This variable is buffer-local.")
 164
 165 (defvar ielm-header
 166   "*** Welcome to IELM ***  Type (describe-mode) for help.\n"
 167   "Message to display when IELM is started.")
 168
 169 (defvar ielm-map
 170   (let ((map (make-sparse-keymap)))
 171     (define-key map "\t" 'comint-dynamic-complete)
 172     (define-key map "\C-m" 'ielm-return)
 173     (define-key map "\C-j" 'ielm-send-input)
 174     (define-key map "\e\C-x" 'eval-defun)         ; for consistency with
 175     (define-key map "\e\t" 'completion-at-point)  ; lisp-interaction-mode
 176     ;; These bindings are from `lisp-mode-shared-map' -- can you inherit
 177     ;; from more than one keymap??
 178     (define-key map "\e\C-q" 'indent-sexp)
 179     (define-key map "\177" 'backward-delete-char-untabify)
 180     ;; Some convenience bindings for setting the working buffer
 181     (define-key map "\C-c\C-b" 'ielm-change-working-buffer)
 182     (define-key map "\C-c\C-f" 'ielm-display-working-buffer)
 183     (define-key map "\C-c\C-v" 'ielm-print-working-buffer)
 184     map)
 185   "Keymap for IELM mode.")
 186 (defvaralias 'inferior-emacs-lisp-mode-map 'ielm-map)
 187
 188 (defvar ielm-font-lock-keywords
 189   '(("\\(^\\*\\*\\*[^*]+\\*\\*\\*\\)\\(.*$\\)"
 190      (1 font-lock-comment-face)
 191      (2 font-lock-constant-face)))
 192   "Additional expressions to highlight in IELM buffers.")
 193
 194 ;;; Completion stuff
 195
 196 (defun ielm-tab nil
 197   "Possibly indent the current line as Lisp code."
 198   (interactive)
 199   (when (or (eq (preceding-char) ?\n)
 200             (eq (char-syntax (preceding-char)) ?\s))
 201     (ielm-indent-line)
 202     t))
 203
 204 (defun ielm-complete-symbol nil
 205   "Complete the Lisp symbol before point."
 206   ;; A wrapper for lisp-complete symbol that returns non-nil if
 207   ;; completion has occurred
 208   (let* ((btick (buffer-modified-tick))
 209          (cbuffer (get-buffer "*Completions*"))
 210          (ctick (and cbuffer (buffer-modified-tick cbuffer))))
 211     (lisp-complete-symbol)
 212      ;; completion has occurred if:
 213     (or
 214      ;; the buffer has been modified
 215      (not (= btick (buffer-modified-tick)))
 216      ;; a completions buffer has been modified or created
 217      (if cbuffer
 218          (not (= ctick (buffer-modified-tick cbuffer)))
 219        (get-buffer "*Completions*")))))
 220
 221 (defun ielm-complete-filename nil
 222   "Dynamically complete filename before point, if in a string."
 223   (when (nth 3 (parse-partial-sexp comint-last-input-start (point)))
 224     (comint-dynamic-complete-filename)))
 225
 226 (defun ielm-indent-line nil
 227   "Indent the current line as Lisp code if it is not a prompt line."
 228   (when (save-excursion (comint-bol) (bolp))
 229     (lisp-indent-line)))
 230
 231 ;;; Working buffer manipulation
 232
 233 (defun ielm-print-working-buffer nil
 234   "Print the current IELM working buffer's name in the echo area."
 235   (interactive)
 236   (message "The current working buffer is: %s" (buffer-name ielm-working-buffer)))
 237
 238 (defun ielm-display-working-buffer nil
 239   "Display the current IELM working buffer.
 240 Don't forget that selecting that buffer will change its value of `point'
 241 to its value of `window-point'!"
 242   (interactive)
 243   (display-buffer ielm-working-buffer)
 244   (ielm-print-working-buffer))
 245
 246 (defun ielm-change-working-buffer (buf)
 247   "Change the current IELM working buffer to BUF.
 248 This is the buffer in which all sexps entered at the IELM prompt are
 249 evaluated.  You can achieve the same effect with a call to
 250 `set-buffer' at the IELM prompt."
 251   (interactive "bSet working buffer to: ")
 252   (let ((buffer (get-buffer buf)))
 253     (if (and buffer (buffer-live-p buffer))
 254         (setq ielm-working-buffer buffer)
 255       (error "No such buffer: %S" buf)))
 256   (ielm-print-working-buffer))
 257
 258 ;;; Other bindings
 259
 260 (defun ielm-return nil
 261   "Newline and indent, or evaluate the sexp before the prompt.
 262 Complete sexps are evaluated; for incomplete sexps inserts a newline
 263 and indents.  If however `ielm-dynamic-return' is nil, this always
 264 simply inserts a newline."
 265   (interactive)
 266   (if ielm-dynamic-return
 267       (let ((state
 268              (save-excursion
 269                (end-of-line)
 270                (parse-partial-sexp (ielm-pm)
 271                                    (point)))))
 272         (if (and (< (car state) 1) (not (nth 3 state)))
 273             (ielm-send-input)
 274           (when (and ielm-dynamic-multiline-inputs
 275                      (save-excursion
 276                        (beginning-of-line)
 277                        (looking-at-p comint-prompt-regexp)))
 278             (save-excursion
 279               (goto-char (ielm-pm))
 280               (newline 1)))
 281           (newline-and-indent)))
 282     (newline)))
 283
 284 (defvar ielm-input)
 285
 286 (defun ielm-input-sender (proc input)
 287   ;; Just sets the variable ielm-input, which is in the scope of
 288   ;; `ielm-send-input's call.
 289   (setq ielm-input input))
 290
 291 (defun ielm-send-input nil
 292   "Evaluate the Emacs Lisp expression after the prompt."
 293   (interactive)
 294   (let (ielm-input)                     ; set by ielm-input-sender
 295     (comint-send-input)                 ; update history, markers etc.
 296     (ielm-eval-input ielm-input)))
 297
 298 ;;; Utility functions
 299
 300 (defun ielm-is-whitespace-or-comment (string)
 301   "Return non-nil if STRING is all whitespace or a comment."
 302   (or (string= string "")
 303       (string-match-p "\\`[ \t\n]*\\(?:;.*\\)*\\'" string)))
 304
 305 ;;; Evaluation
 306
 307 (defun ielm-eval-input (ielm-string)
 308   "Evaluate the Lisp expression IELM-STRING, and pretty-print the result."
 309   ;; This is the function that actually `sends' the input to the
 310   ;; `inferior Lisp process'. All comint-send-input does is works out
 311   ;; what that input is.  What this function does is evaluates that
 312   ;; input and produces `output' which gets inserted into the buffer,
 313   ;; along with a new prompt.  A better way of doing this might have
 314   ;; been to actually send the output to the `cat' process, and write
 315   ;; this as in output filter that converted sexps in the output
 316   ;; stream to their evaluated value.  But that would have involved
 317   ;; more process coordination than I was happy to deal with.
 318   ;;
 319   ;; NOTE: all temporary variables in this function will be in scope
 320   ;; during the eval, and so need to have non-clashing names.
 321   (let (ielm-form                       ; form to evaluate
 322         ielm-pos                        ; End posn of parse in string
 323         ielm-result                     ; Result, or error message
 324         ielm-error-type                 ; string, nil if no error
 325         (ielm-output "")                ; result to display
 326         (ielm-wbuf ielm-working-buffer) ; current buffer after evaluation
 327         (ielm-pmark (ielm-pm)))
 328     (unless (ielm-is-whitespace-or-comment ielm-string)
 329       (condition-case err
 330           (let ((rout (read-from-string ielm-string)))
 331             (setq ielm-form (car rout)
 332                   ielm-pos (cdr rout)))
 333         (error (setq ielm-result (error-message-string err))
 334                (setq ielm-error-type "Read error")))
 335       (unless ielm-error-type
 336         ;; Make sure working buffer has not been killed
 337         (if (not (buffer-name ielm-working-buffer))
 338             (setq ielm-result "Working buffer has been killed"
 339                   ielm-error-type "IELM Error"
 340                   ielm-wbuf (current-buffer))
 341           (if (ielm-is-whitespace-or-comment (substring ielm-string ielm-pos))
 342               ;; To correctly handle the ielm-local variables *,
 343               ;; ** and ***, we need a temporary buffer to be
 344               ;; current at entry to the inner of the next two let
 345               ;; forms.  We need another temporary buffer to exit
 346               ;; that same let.  To avoid problems, neither of
 347               ;; these buffers should be alive during the
 348               ;; evaluation of ielm-form.
 349               (let ((*1 *)
 350                     (*2 **)
 351                     (*3 ***)
 352                     ielm-temp-buffer)
 353                 (set-match-data ielm-match-data)
 354                 (save-excursion
 355                   (with-temp-buffer
 356                     (condition-case err
 357                         (unwind-protect
 358                              ;; The next let form creates default
 359                              ;; bindings for *, ** and ***.  But
 360                              ;; these default bindings are
 361                              ;; identical to the ielm-local
 362                              ;; bindings.  Hence, during the
 363                              ;; evaluation of ielm-form, the
 364                              ;; ielm-local values are going to be
 365                              ;; used in all buffers except for
 366                              ;; other ielm buffers, which override
 367                              ;; them.  Normally, the variables *1,
 368                              ;; *2 and *3 also have default
 369                              ;; bindings, which are not overridden.
 370                              (let ((* *1)
 371                                    (** *2)
 372                                    (*** *3))
 373                                (kill-buffer (current-buffer))
 374                                (set-buffer ielm-wbuf)
 375                                (setq ielm-result (eval ielm-form))
 376                                (setq ielm-wbuf (current-buffer))
 377                                (setq
 378                                 ielm-temp-buffer
 379                                 (generate-new-buffer " *ielm-temp*"))
 380                                (set-buffer ielm-temp-buffer))
 381                           (when ielm-temp-buffer
 382                             (kill-buffer ielm-temp-buffer)))
 383                       (error (setq ielm-result (error-message-string err))
 384                              (setq ielm-error-type "Eval error"))
 385                       (quit (setq ielm-result "Quit during evaluation")
 386                             (setq ielm-error-type "Eval error")))))
 387                 (setq ielm-match-data (match-data)))
 388             (setq ielm-error-type "IELM error")
 389             (setq ielm-result "More than one sexp in input"))))
 390
 391       ;; If the eval changed the current buffer, mention it here
 392       (unless (eq ielm-wbuf ielm-working-buffer)
 393         (message "current buffer is now: %s" ielm-wbuf)
 394         (setq ielm-working-buffer ielm-wbuf))
 395
 396       (goto-char ielm-pmark)
 397       (unless ielm-error-type
 398         (condition-case err
 399             ;; Self-referential objects cause loops in the printer, so
 400             ;; trap quits here. May as well do errors, too
 401             (setq ielm-output (concat ielm-output (pp-to-string ielm-result)))
 402           (error (setq ielm-error-type "IELM Error")
 403                  (setq ielm-result "Error during pretty-printing (bug in pp)"))
 404           (quit  (setq ielm-error-type "IELM Error")
 405                  (setq ielm-result "Quit during pretty-printing"))))
 406       (if ielm-error-type
 407           (progn
 408             (when ielm-noisy (ding))
 409             (setq ielm-output (concat ielm-output "*** " ielm-error-type " ***  "))
 410             (setq ielm-output (concat ielm-output ielm-result)))
 411         ;; There was no error, so shift the *** values
 412         (setq *** **)
 413         (setq ** *)
 414         (setq * ielm-result))
 415       (setq ielm-output (concat ielm-output "\n")))
 416     (setq ielm-output (concat ielm-output ielm-prompt-internal))
 417     (comint-output-filter (ielm-process) ielm-output)))
 418
 419 ;;; Process and marker utilities
 420
 421 (defun ielm-process nil
 422   ;; Return the current buffer's process.
 423   (get-buffer-process (current-buffer)))
 424
 425 (defun ielm-pm nil
 426   ;; Return the process mark of the current buffer.
 427   (process-mark (get-buffer-process (current-buffer))))
 428
 429 (defun ielm-set-pm (pos)
 430   ;; Set the process mark in the current buffer to POS.
 431   (set-marker (process-mark (get-buffer-process (current-buffer))) pos))
 432
 433 ;;; Major mode
 434
 435 (define-derived-mode inferior-emacs-lisp-mode comint-mode "IELM"
 436   "Major mode for interactively evaluating Emacs Lisp expressions.
 437 Uses the interface provided by `comint-mode' (which see).
 438
 439 * \\<ielm-map>\\[ielm-send-input] evaluates the sexp following the prompt.  There must be at most
 440   one top level sexp per prompt.
 441
 442 * \\[ielm-return] inserts a newline and indents, or evaluates a
 443   complete expression (but see variable `ielm-dynamic-return').
 444   Inputs longer than one line are moved to the line following the
 445   prompt (but see variable `ielm-dynamic-multiline-inputs').
 446
 447 * \\[comint-dynamic-complete] completes Lisp symbols (or filenames, within strings),
 448   or indents the line if there is nothing to complete.
 449
 450 The current working buffer may be changed (with a call to `set-buffer',
 451 or with \\[ielm-change-working-buffer]), and its value is preserved between successive
 452 evaluations.  In this way, expressions may be evaluated in a different
 453 buffer than the *ielm* buffer.  By default, its name is shown on the
 454 mode line; you can always display it with \\[ielm-print-working-buffer], or the buffer itself
 455 with \\[ielm-display-working-buffer].
 456
 457 During evaluations, the values of the variables `*', `**', and `***'
 458 are the results of the previous, second previous and third previous
 459 evaluations respectively.  If the working buffer is another IELM
 460 buffer, then the values in the working buffer are used.  The variables
 461 `*1', `*2' and `*3', yield the process buffer values.
 462
 463 Expressions evaluated by IELM are not subject to `debug-on-quit' or
 464 `debug-on-error'.
 465
 466 The behavior of IELM may be customized with the following variables:
 467 * To stop beeping on error, set `ielm-noisy' to nil.
 468 * If you don't like the prompt, you can change it by setting `ielm-prompt'.
 469 * If you do not like that the prompt is (by default) read-only, set
 470   `ielm-prompt-read-only' to nil.
 471 * Set `ielm-dynamic-return' to nil for bindings like `lisp-interaction-mode'.
 472 * Entry to this mode runs `comint-mode-hook' and `ielm-mode-hook'
 473  (in that order).
 474
 475 Customized bindings may be defined in `ielm-map', which currently contains:
 476 \\{ielm-map}"
 477   :syntax-table emacs-lisp-mode-syntax-table
 478
 479   (setq comint-prompt-regexp (concat "^" (regexp-quote ielm-prompt)))
 480   (set (make-local-variable 'paragraph-separate) "\\'")
 481   (set (make-local-variable 'paragraph-start) comint-prompt-regexp)
 482   (setq comint-input-sender 'ielm-input-sender)
 483   (setq comint-process-echoes nil)
 484   (set (make-local-variable 'comint-dynamic-complete-functions)
 485        '(ielm-tab comint-replace-by-expanded-history
 486          ielm-complete-filename ielm-complete-symbol))
 487   (set (make-local-variable 'ielm-prompt-internal) ielm-prompt)
 488   (set (make-local-variable 'comint-prompt-read-only) ielm-prompt-read-only)
 489   (setq comint-get-old-input 'ielm-get-old-input)
 490   (set (make-local-variable 'comint-completion-addsuffix) '("/" . ""))
 491   (setq mode-line-process '(":%s on " (:eval (buffer-name ielm-working-buffer))))
 492
 493   (set (make-local-variable 'indent-line-function) 'ielm-indent-line)
 494   (set (make-local-variable 'ielm-working-buffer) (current-buffer))
 495   (set (make-local-variable 'fill-paragraph-function) 'lisp-fill-paragraph)
 496   (add-hook 'completion-at-point-functions
 497             'lisp-completion-at-point nil 'local)
 498
 499   ;; Value holders
 500   (set (make-local-variable '*) nil)
 501   (set (make-local-variable '**) nil)
 502   (set (make-local-variable '***) nil)
 503   (set (make-local-variable 'ielm-match-data) nil)
 504
 505   ;; font-lock support
 506   (set (make-local-variable 'font-lock-defaults)
 507        '(ielm-font-lock-keywords nil nil ((?: . "w") (?- . "w") (?* . "w"))))
 508
 509   ;; A dummy process to keep comint happy. It will never get any input
 510   (unless (comint-check-proc (current-buffer))
 511     ;; Was cat, but on non-Unix platforms that might not exist, so
 512     ;; use hexl instead, which is part of the Emacs distribution.
 513     (condition-case nil
 514         (start-process "ielm" (current-buffer) "hexl")
 515       (file-error (start-process "ielm" (current-buffer) "cat")))
 516     (set-process-query-on-exit-flag (ielm-process) nil)
 517     (goto-char (point-max))
 518
 519     ;; Lisp output can include raw characters that confuse comint's
 520     ;; carriage control code.
 521     (set (make-local-variable 'comint-inhibit-carriage-motion) t)
 522
 523     ;; Add a silly header
 524     (insert ielm-header)
 525     (ielm-set-pm (point-max))
 526     (unless comint-use-prompt-regexp
 527       (let ((inhibit-read-only t))
 528         (add-text-properties
 529          (point-min) (point-max)
 530          '(rear-nonsticky t field output inhibit-line-move-field-capture t))))
 531     (comint-output-filter (ielm-process) ielm-prompt-internal)
 532     (set-marker comint-last-input-start (ielm-pm))
 533     (set-process-filter (get-buffer-process (current-buffer)) 'comint-output-filter)))
 534
 535 (defun ielm-get-old-input nil
 536   ;; Return the previous input surrounding point
 537   (save-excursion
 538     (beginning-of-line)
 539     (unless (looking-at-p comint-prompt-regexp)
 540       (re-search-backward comint-prompt-regexp))
 541     (comint-skip-prompt)
 542     (buffer-substring (point) (progn (forward-sexp 1) (point)))))
 543
 544 ;;; User command
 545
 546 ;;;###autoload (add-hook 'same-window-buffer-names (purecopy "*ielm*"))
 547
 548 ;;;###autoload
 549 (defun ielm nil
 550   "Interactively evaluate Emacs Lisp expressions.
 551 Switches to the buffer `*ielm*', or creates it if it does not exist."
 552   (interactive)
 553   (let (old-point)
 554     (unless (comint-check-proc "*ielm*")
 555       (with-current-buffer (get-buffer-create "*ielm*")
 556         (unless (zerop (buffer-size)) (setq old-point (point)))
 557         (inferior-emacs-lisp-mode)))
 558     (pop-to-buffer "*ielm*")
 559     (when old-point (push-mark old-point))))
 560
 561 (provide 'ielm)
 562
 563 ;; arch-tag: ef60e4c0-9c4f-4bdb-8402-271313329790
 564 ;;; ielm.el ends here