lisp/xscheme.el

   1 ;;; xscheme.el --- run MIT Scheme under Emacs
   2
   3 ;; Copyright (C) 1986, 1987, 1989, 1990, 2001 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: languages, lisp
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; A major mode for interacting with MIT Scheme.
  28 ;;
  29 ;; Requires MIT Scheme release 5 or later.
  30 ;; Changes to Control-G handler require runtime version 13.85 or later.
  31
  32 ;;; Code:
  33
  34 (require 'scheme)
  35 \f
  36 (defgroup xscheme nil
  37   "Major mode for editing Scheme and interacting with MIT's C-Scheme."
  38   :group 'lisp)
  39
  40 (defcustom scheme-band-name nil
  41   "*Band loaded by the `run-scheme' command."
  42   :type '(choice (const nil) string)
  43   :group 'xscheme)
  44
  45 (defcustom scheme-program-arguments nil
  46   "*Arguments passed to the Scheme program by the `run-scheme' command."
  47   :type '(choice (const nil) string)
  48   :group 'xscheme)
  49
  50 (defcustom xscheme-allow-pipelined-evaluation t
  51   "If non-nil, an expression may be transmitted while another is evaluating.
  52 Otherwise, attempting to evaluate an expression before the previous expression
  53 has finished evaluating will signal an error."
  54   :type 'boolean
  55   :group 'xscheme)
  56
  57 (defcustom xscheme-startup-message
  58   "This is the Scheme process buffer.
  59 Type \\[advertised-xscheme-send-previous-expression] to evaluate the expression before point.
  60 Type \\[xscheme-send-control-g-interrupt] to abort evaluation.
  61 Type \\[describe-mode] for more information.
  62
  63 "
  64   "String to insert into Scheme process buffer first time it is started.
  65 Is processed with `substitute-command-keys' first."
  66   :type 'string
  67   :group 'xscheme)
  68
  69 (defcustom xscheme-signal-death-message nil
  70   "If non-nil, causes a message to be generated when the Scheme process dies."
  71   :type 'boolean
  72   :group 'xscheme)
  73
  74 (defcustom xscheme-start-hook nil
  75   "If non-nil, a procedure to call when the Scheme process is started.
  76 When called, the current buffer will be the Scheme process-buffer."
  77   :type 'hook
  78   :group 'xscheme
  79   :version "20.3")
  80
  81 (defun xscheme-evaluation-commands (keymap)
  82   (define-key keymap "\e\C-x" 'xscheme-send-definition)
  83   (define-key keymap "\C-x\C-e" 'advertised-xscheme-send-previous-expression)
  84   (define-key keymap "\eo" 'xscheme-send-buffer)
  85   (define-key keymap "\ez" 'xscheme-send-definition)
  86   (define-key keymap "\e\C-m" 'xscheme-send-previous-expression)
  87   (define-key keymap "\e\C-z" 'xscheme-send-region))
  88
  89 (defun xscheme-interrupt-commands (keymap)
  90   (define-key keymap "\C-c\C-s" 'xscheme-select-process-buffer)
  91   (define-key keymap "\C-c\C-b" 'xscheme-send-breakpoint-interrupt)
  92   (define-key keymap "\C-c\C-c" 'xscheme-send-control-g-interrupt)
  93   (define-key keymap "\C-c\C-u" 'xscheme-send-control-u-interrupt)
  94   (define-key keymap "\C-c\C-x" 'xscheme-send-control-x-interrupt))
  95
  96 (xscheme-evaluation-commands scheme-mode-map)
  97 (xscheme-interrupt-commands scheme-mode-map)
  98 \f
  99 (defun run-scheme (command-line)
 100   "Run MIT Scheme in an inferior process.
 101 Output goes to the buffer `*scheme*'.
 102 With argument, asks for a command line."
 103   (interactive (list (xscheme-read-command-line current-prefix-arg)))
 104   (xscheme-start command-line xscheme-process-name xscheme-buffer-name))
 105
 106 (defun xscheme-start (command-line process-name buffer-name)
 107   (setq-default xscheme-process-command-line command-line)
 108   (switch-to-buffer
 109    (xscheme-start-process command-line process-name buffer-name))
 110   (make-local-variable 'xscheme-process-command-line)
 111   (setq xscheme-process-command-line command-line))
 112
 113 (defun xscheme-read-command-line (arg)
 114   (let ((default
 115           (or xscheme-process-command-line
 116               (xscheme-default-command-line))))
 117     (if arg
 118         (read-string "Run Scheme: " default)
 119         default)))
 120
 121 (defun xscheme-default-command-line ()
 122   (concat scheme-program-name " -emacs"
 123           (if scheme-program-arguments
 124               (concat " " scheme-program-arguments)
 125               "")
 126           (if scheme-band-name
 127               (concat " -band " scheme-band-name)
 128               "")))
 129
 130 (defun reset-scheme ()
 131   "Reset the Scheme process."
 132   (interactive)
 133   (let ((process (get-process xscheme-process-name)))
 134     (cond ((or (not process)
 135                (not (eq (process-status process) 'run))
 136                (yes-or-no-p
 137 "The Scheme process is running, are you SURE you want to reset it? "))
 138            (message "Resetting Scheme process...")
 139            (if process
 140                (progn
 141                  (kill-process process t)
 142                  (delete-process process)))
 143            (xscheme-start-process xscheme-process-command-line
 144                                   xscheme-process-name
 145                                   xscheme-buffer-name)
 146            (message "Resetting Scheme process...done")))))
 147 \f
 148 ;;;; Multiple Scheme buffer management commands
 149
 150 (defun start-scheme (buffer-name &optional globally)
 151   "Choose a scheme interaction buffer, or create a new one."
 152   ;; (interactive "BScheme interaction buffer: \nP")
 153   (interactive
 154    (list (read-buffer "Scheme interaction buffer: "
 155                       xscheme-buffer-name
 156                       nil)
 157          current-prefix-arg))
 158   (let ((buffer (get-buffer-create buffer-name)))
 159     (let ((process (get-buffer-process buffer)))
 160       (if process
 161           (switch-to-buffer buffer)
 162         (if (or (not (buffer-file-name buffer))
 163                 (yes-or-no-p (concat "Buffer "
 164                                      (buffer-name buffer)
 165                                      " contains file "
 166                                      (buffer-file-name buffer)
 167                                      "; start scheme in it? ")))
 168             (progn
 169               (xscheme-start (xscheme-read-command-line t)
 170                              buffer-name
 171                              buffer-name)
 172               (if globally
 173                   (global-set-scheme-interaction-buffer buffer-name)))
 174           (message "start-scheme aborted"))))))
 175
 176 (fset 'select-scheme 'start-scheme)
 177
 178 (defun global-set-scheme-interaction-buffer (buffer-name)
 179   "Set the default scheme interaction buffer."
 180   (interactive
 181    (list (read-buffer "Scheme interaction buffer: "
 182                       xscheme-buffer-name
 183                       t)))
 184   (let ((process-name (verify-xscheme-buffer buffer-name nil)))
 185     (setq-default xscheme-buffer-name buffer-name)
 186     (setq-default xscheme-process-name process-name)
 187     (setq-default xscheme-runlight-string
 188                   (save-excursion (set-buffer buffer-name)
 189                                   xscheme-runlight-string))
 190     (setq-default xscheme-runlight
 191                   (if (eq (process-status process-name) 'run)
 192                       default-xscheme-runlight
 193                       ""))))
 194
 195 (defun local-set-scheme-interaction-buffer (buffer-name)
 196   "Set the scheme interaction buffer for the current buffer."
 197   (interactive
 198    (list (read-buffer "Scheme interaction buffer: "
 199                       xscheme-buffer-name
 200                       t)))
 201   (let ((process-name (verify-xscheme-buffer buffer-name t)))
 202     (make-local-variable 'xscheme-buffer-name)
 203     (setq xscheme-buffer-name buffer-name)
 204     (make-local-variable 'xscheme-process-name)
 205     (setq xscheme-process-name process-name)
 206     (make-local-variable 'xscheme-runlight)
 207     (setq xscheme-runlight (save-excursion (set-buffer buffer-name)
 208                                            xscheme-runlight))))
 209
 210 (defun local-clear-scheme-interaction-buffer ()
 211   "Make the current buffer use the default scheme interaction buffer."
 212   (interactive)
 213   (if (xscheme-process-buffer-current-p)
 214       (error "Cannot change the interaction buffer of an interaction buffer"))
 215   (kill-local-variable 'xscheme-buffer-name)
 216   (kill-local-variable 'xscheme-process-name)
 217   (kill-local-variable 'xscheme-runlight))
 218
 219 (defun verify-xscheme-buffer (buffer-name localp)
 220   (if (and localp (xscheme-process-buffer-current-p))
 221       (error "Cannot change the interaction buffer of an interaction buffer"))
 222   (let* ((buffer (get-buffer buffer-name))
 223          (process (and buffer (get-buffer-process buffer))))
 224     (cond ((not buffer)
 225            (error "Buffer does not exist" buffer-name))
 226           ((not process)
 227            (error "Buffer is not a scheme interaction buffer" buffer-name))
 228           (t
 229            (save-excursion
 230              (set-buffer buffer)
 231              (if (not (xscheme-process-buffer-current-p))
 232                  (error "Buffer is not a scheme interaction buffer"
 233                         buffer-name)))
 234            (process-name process)))))
 235 \f
 236 ;;;; Interaction Mode
 237
 238 (defun scheme-interaction-mode (&optional preserve)
 239   "Major mode for interacting with an inferior MIT Scheme process.
 240 Like  scheme-mode  except that:
 241
 242 \\[advertised-xscheme-send-previous-expression] sends the expression before point to the Scheme process as input
 243 \\[xscheme-yank-pop] yanks an expression previously sent to Scheme
 244 \\[xscheme-yank-push] yanks an expression more recently sent to Scheme
 245
 246 All output from the Scheme process is written in the Scheme process
 247 buffer, which is initially named \"*scheme*\".  The result of
 248 evaluating a Scheme expression is also printed in the process buffer,
 249 preceded by the string \";Value: \" to highlight it.  If the process
 250 buffer is not visible at that time, the value will also be displayed
 251 in the minibuffer.  If an error occurs, the process buffer will
 252 automatically pop up to show you the error message.
 253
 254 While the Scheme process is running, the modelines of all buffers in
 255 scheme-mode are modified to show the state of the process.  The
 256 possible states and their meanings are:
 257
 258 input           waiting for input
 259 run             evaluating
 260 gc              garbage collecting
 261
 262 The process buffer's modeline contains additional information where
 263 the buffer's name is normally displayed: the command interpreter level
 264 and type.
 265
 266 Scheme maintains a stack of command interpreters.  Every time an error
 267 or breakpoint occurs, the current command interpreter is pushed on the
 268 command interpreter stack, and a new command interpreter is started.
 269 One example of why this is done is so that an error that occurs while
 270 you are debugging another error will not destroy the state of the
 271 initial error, allowing you to return to it after the second error has
 272 been fixed.
 273
 274 The command interpreter level indicates how many interpreters are in
 275 the command interpreter stack.  It is initially set to one, and it is
 276 incremented every time that stack is pushed, and decremented every
 277 time it is popped.  The following commands are useful for manipulating
 278 the command interpreter stack:
 279
 280 \\[xscheme-send-breakpoint-interrupt]   pushes the stack once
 281 \\[xscheme-send-control-u-interrupt]    pops the stack once
 282 \\[xscheme-send-control-g-interrupt]    pops everything off
 283 \\[xscheme-send-control-x-interrupt]    aborts evaluation, doesn't affect stack
 284
 285 Some possible command interpreter types and their meanings are:
 286
 287 [Evaluator]     read-eval-print loop for evaluating expressions
 288 [Debugger]      single character commands for debugging errors
 289 [Where]         single character commands for examining environments
 290
 291 Starting with release 6.2 of Scheme, the latter two types of command
 292 interpreters will change the major mode of the Scheme process buffer
 293 to scheme-debugger-mode , in which the evaluation commands are
 294 disabled, and the keys which normally self insert instead send
 295 themselves to the Scheme process.  The command character ? will list
 296 the available commands.
 297
 298 For older releases of Scheme, the major mode will be be
 299 scheme-interaction-mode , and the command characters must be sent as
 300 if they were expressions.
 301
 302 Commands:
 303 Delete converts tabs to spaces as it moves back.
 304 Blank lines separate paragraphs.  Semicolons start comments.
 305 \\{scheme-interaction-mode-map}
 306
 307 Entry to this mode calls the value of scheme-interaction-mode-hook
 308 with no args, if that value is non-nil.
 309  Likewise with the value of scheme-mode-hook.
 310  scheme-interaction-mode-hook is called after scheme-mode-hook."
 311   (interactive "P")
 312   (if (not preserve)
 313       (let ((previous-mode major-mode))
 314         (kill-all-local-variables)
 315         (make-local-variable 'xscheme-previous-mode)
 316         (make-local-variable 'xscheme-buffer-name)
 317         (make-local-variable 'xscheme-process-name)
 318         (make-local-variable 'xscheme-previous-process-state)
 319         (make-local-variable 'xscheme-runlight-string)
 320         (make-local-variable 'xscheme-runlight)
 321         (make-local-variable 'xscheme-last-input-end)
 322         (setq xscheme-previous-mode previous-mode)
 323         (let ((buffer (current-buffer)))
 324           (setq xscheme-buffer-name (buffer-name buffer))
 325           (setq xscheme-last-input-end (make-marker))
 326           (let ((process (get-buffer-process buffer)))
 327             (if process
 328                 (progn
 329                   (setq xscheme-process-name (process-name process))
 330                   (setq xscheme-previous-process-state
 331                         (cons (process-filter process)
 332                               (process-sentinel process)))
 333                   (xscheme-process-filter-initialize t)
 334                   (xscheme-modeline-initialize xscheme-buffer-name)
 335                   (set-process-sentinel process 'xscheme-process-sentinel)
 336                   (set-process-filter process 'xscheme-process-filter))
 337                 (setq xscheme-previous-process-state (cons nil nil)))))))
 338   (scheme-interaction-mode-initialize)
 339   (scheme-mode-variables)
 340   (run-hooks 'scheme-mode-hook 'scheme-interaction-mode-hook))
 341
 342 (defun exit-scheme-interaction-mode ()
 343   "Take buffer out of scheme interaction mode"
 344   (interactive)
 345   (if (not (eq major-mode 'scheme-interaction-mode))
 346       (error "Buffer not in scheme interaction mode"))
 347   (let ((previous-state xscheme-previous-process-state))
 348     (funcall xscheme-previous-mode)
 349     (let ((process (get-buffer-process (current-buffer))))
 350       (if process
 351           (progn
 352             (if (eq (process-filter process) 'xscheme-process-filter)
 353                 (set-process-filter process (car previous-state)))
 354             (if (eq (process-sentinel process) 'xscheme-process-sentinel)
 355                 (set-process-sentinel process (cdr previous-state))))))))
 356
 357 (defun scheme-interaction-mode-initialize ()
 358   (use-local-map scheme-interaction-mode-map)
 359   (setq major-mode 'scheme-interaction-mode)
 360   (setq mode-name "Scheme Interaction"))
 361
 362 (defun scheme-interaction-mode-commands (keymap)
 363   (let ((entries scheme-interaction-mode-commands-alist))
 364     (while entries
 365       (define-key keymap
 366         (car (car entries))
 367         (car (cdr (car entries))))
 368       (setq entries (cdr entries)))))
 369
 370 (defvar scheme-interaction-mode-commands-alist nil)
 371 (setq scheme-interaction-mode-commands-alist
 372       (append scheme-interaction-mode-commands-alist
 373               '(("\C-c\C-m" xscheme-send-current-line)
 374                 ("\C-c\C-o" xscheme-delete-output)
 375                 ("\C-c\C-p" xscheme-send-proceed)
 376                 ("\C-c\C-y" xscheme-yank)
 377                 ("\ep" xscheme-yank-pop)
 378                 ("\en" xscheme-yank-push))))
 379
 380 (defvar scheme-interaction-mode-map nil)
 381 (if (not scheme-interaction-mode-map)
 382     (progn
 383       (setq scheme-interaction-mode-map (make-keymap))
 384       (scheme-mode-commands scheme-interaction-mode-map)
 385       (xscheme-interrupt-commands scheme-interaction-mode-map)
 386       (xscheme-evaluation-commands scheme-interaction-mode-map)
 387       (scheme-interaction-mode-commands scheme-interaction-mode-map)))
 388
 389 (defun xscheme-enter-interaction-mode ()
 390   (save-excursion
 391     (set-buffer (xscheme-process-buffer))
 392     (if (not (eq major-mode 'scheme-interaction-mode))
 393         (if (eq major-mode 'scheme-debugger-mode)
 394             (scheme-interaction-mode-initialize)
 395             (scheme-interaction-mode t)))))
 396
 397 (fset 'advertised-xscheme-send-previous-expression
 398       'xscheme-send-previous-expression)
 399 \f
 400 ;;;; Debugger Mode
 401
 402 (defun scheme-debugger-mode ()
 403   "Major mode for executing the Scheme debugger.
 404 Like  scheme-mode  except that the evaluation commands
 405 are disabled, and characters that would normally be self inserting are
 406 sent to the Scheme process instead.  Typing ?  will show you which
 407 characters perform useful functions.
 408
 409 Commands:
 410 \\{scheme-debugger-mode-map}"
 411   (error "Illegal entry to scheme-debugger-mode"))
 412
 413 (defun scheme-debugger-mode-initialize ()
 414   (use-local-map scheme-debugger-mode-map)
 415   (setq major-mode 'scheme-debugger-mode)
 416   (setq mode-name "Scheme Debugger"))
 417
 418 (defun scheme-debugger-mode-commands (keymap)
 419   (let ((char ? ))
 420     (while (< char 127)
 421       (define-key keymap (char-to-string char) 'scheme-debugger-self-insert)
 422       (setq char (1+ char)))))
 423
 424 (defvar scheme-debugger-mode-map nil)
 425 (if (not scheme-debugger-mode-map)
 426     (progn
 427       (setq scheme-debugger-mode-map (make-keymap))
 428       (scheme-mode-commands scheme-debugger-mode-map)
 429       (xscheme-interrupt-commands scheme-debugger-mode-map)
 430       (scheme-debugger-mode-commands scheme-debugger-mode-map)))
 431
 432 (defun scheme-debugger-self-insert ()
 433   "Transmit this character to the Scheme process."
 434   (interactive)
 435   (xscheme-send-char last-command-char))
 436
 437 (defun xscheme-enter-debugger-mode (prompt-string)
 438   (save-excursion
 439     (set-buffer (xscheme-process-buffer))
 440     (if (not (eq major-mode 'scheme-debugger-mode))
 441         (progn
 442           (if (not (eq major-mode 'scheme-interaction-mode))
 443               (scheme-interaction-mode t))
 444           (scheme-debugger-mode-initialize)))))
 445
 446 (defun xscheme-debugger-mode-p ()
 447   (let ((buffer (xscheme-process-buffer)))
 448     (and buffer
 449          (save-excursion
 450            (set-buffer buffer)
 451            (eq major-mode 'scheme-debugger-mode)))))
 452 \f
 453 ;;;; Evaluation Commands
 454
 455 (defun xscheme-send-string (&rest strings)
 456   "Send the string arguments to the Scheme process.
 457 The strings are concatenated and terminated by a newline."
 458   (cond ((not (xscheme-process-running-p))
 459          (if (yes-or-no-p "The Scheme process has died.  Reset it? ")
 460              (progn
 461                (reset-scheme)
 462                (xscheme-wait-for-process)
 463                (xscheme-send-string-1 strings))))
 464         ((xscheme-debugger-mode-p) (error "No sends allowed in debugger mode"))
 465         ((and (not xscheme-allow-pipelined-evaluation)
 466               xscheme-running-p)
 467          (error "No sends allowed while Scheme running"))
 468         (t (xscheme-send-string-1 strings))))
 469
 470 (defun xscheme-send-string-1 (strings)
 471   (let ((string (apply 'concat strings)))
 472     (xscheme-send-string-2 string)
 473     (if (eq major-mode 'scheme-interaction-mode)
 474         (xscheme-insert-expression string))))
 475
 476 (defun xscheme-send-string-2 (string)
 477   (let ((process (get-process xscheme-process-name)))
 478     (process-send-string process (concat string "\n"))
 479     (if (xscheme-process-buffer-current-p)
 480         (set-marker (process-mark process) (point)))))
 481
 482 (defun xscheme-select-process-buffer ()
 483   "Select the Scheme process buffer and move to its output point."
 484   (interactive)
 485   (let ((process
 486          (or (get-process xscheme-process-name)
 487              (error "No scheme process"))))
 488     (let ((buffer (or (process-buffer process) (error "No process buffer"))))
 489       (let ((window (get-buffer-window buffer)))
 490         (if window
 491             (select-window window)
 492             (switch-to-buffer buffer))
 493         (goto-char (process-mark process))))))
 494 \f
 495 ;;;; Scheme expressions ring
 496
 497 (defun xscheme-insert-expression (string)
 498   (setq xscheme-expressions-ring (cons string xscheme-expressions-ring))
 499   (if (> (length xscheme-expressions-ring) xscheme-expressions-ring-max)
 500       (setcdr (nthcdr (1- xscheme-expressions-ring-max)
 501                       xscheme-expressions-ring)
 502               nil))
 503   (setq xscheme-expressions-ring-yank-pointer xscheme-expressions-ring))
 504
 505 (defun xscheme-rotate-yank-pointer (arg)
 506   "Rotate the yanking point in the kill ring."
 507   (interactive "p")
 508   (let ((length (length xscheme-expressions-ring)))
 509     (if (zerop length)
 510         (error "Scheme expression ring is empty")
 511         (setq xscheme-expressions-ring-yank-pointer
 512               (let ((index
 513                      (% (+ arg
 514                            (- length
 515                               (length xscheme-expressions-ring-yank-pointer)))
 516                         length)))
 517                 (nthcdr (if (< index 0)
 518                             (+ index length)
 519                             index)
 520                         xscheme-expressions-ring))))))
 521
 522 (defun xscheme-yank (&optional arg)
 523   "Insert the most recent expression at point.
 524 With just C-U as argument, same but put point in front (and mark at end).
 525 With argument n, reinsert the nth most recently sent expression.
 526 See also the commands \\[xscheme-yank-pop] and \\[xscheme-yank-push]."
 527   (interactive "*P")
 528   (xscheme-rotate-yank-pointer (if (listp arg) 0
 529                                  (if (eq arg '-) -1
 530                                    (1- arg))))
 531   (push-mark (point))
 532   (insert (car xscheme-expressions-ring-yank-pointer))
 533   (if (consp arg)
 534       (exchange-point-and-mark)))
 535
 536 ;; Old name, to avoid errors in users' init files.
 537 (fset 'xscheme-yank-previous-send
 538       'xscheme-yank)
 539
 540 (defun xscheme-yank-pop (arg)
 541   "Insert or replace a just-yanked expression with an older expression.
 542 If the previous command was not a yank, it yanks.
 543 Otherwise, the region contains a stretch of reinserted
 544 expression.  yank-pop deletes that text and inserts in its
 545 place a different expression.
 546
 547 With no argument, the next older expression is inserted.
 548 With argument n, the n'th older expression is inserted.
 549 If n is negative, this is a more recent expression.
 550
 551 The sequence of expressions wraps around, so that after the oldest one
 552 comes the newest one."
 553   (interactive "*p")
 554   (setq this-command 'xscheme-yank)
 555   (if (not (eq last-command 'xscheme-yank))
 556       (progn
 557         (xscheme-yank)
 558         (setq arg (- arg 1))))
 559   (if (not (= arg 0))
 560       (let ((before (< (point) (mark))))
 561         (delete-region (point) (mark))
 562         (xscheme-rotate-yank-pointer arg)
 563         (set-mark (point))
 564         (insert (car xscheme-expressions-ring-yank-pointer))
 565         (if before (exchange-point-and-mark)))))
 566
 567 (defun xscheme-yank-push (arg)
 568   "Insert or replace a just-yanked expression with a more recent expression.
 569 If the previous command was not a yank, it yanks.
 570 Otherwise, the region contains a stretch of reinserted
 571 expression.  yank-pop deletes that text and inserts in its
 572 place a different expression.
 573
 574 With no argument, the next more recent expression is inserted.
 575 With argument n, the n'th more recent expression is inserted.
 576 If n is negative, a less recent expression is used.
 577
 578 The sequence of expressions wraps around, so that after the oldest one
 579 comes the newest one."
 580   (interactive "*p")
 581   (xscheme-yank-pop (- 0 arg)))
 582 \f
 583 (defun xscheme-send-region (start end)
 584   "Send the current region to the Scheme process.
 585 The region is sent terminated by a newline."
 586   (interactive "r")
 587   (if (xscheme-process-buffer-current-p)
 588       (progn
 589         (goto-char end)
 590         (if (not (bolp))
 591             (insert-before-markers ?\n))
 592         (set-marker (process-mark (get-process xscheme-process-name))
 593                     (point))
 594         (set-marker xscheme-last-input-end (point))))
 595   (xscheme-send-string (buffer-substring start end)))
 596
 597 (defun xscheme-send-definition ()
 598   "Send the current definition to the Scheme process.
 599 If the current line begins with a non-whitespace character,
 600 parse an expression from the beginning of the line and send that instead."
 601   (interactive)
 602   (let ((start nil) (end nil))
 603     (save-excursion
 604       (end-of-defun)
 605       (setq end (point))
 606       (if (re-search-backward "^\\s(" nil t)
 607           (setq start (point))
 608           (error "Can't find definition")))
 609     (xscheme-send-region start end)))
 610
 611 (defun xscheme-send-next-expression ()
 612   "Send the expression to the right of `point' to the Scheme process."
 613   (interactive)
 614   (let ((start (point)))
 615     (xscheme-send-region start (save-excursion (forward-sexp) (point)))))
 616
 617 (defun xscheme-send-previous-expression ()
 618   "Send the expression to the left of `point' to the Scheme process."
 619   (interactive)
 620   (let ((end (point)))
 621     (xscheme-send-region (save-excursion (backward-sexp) (point)) end)))
 622 \f
 623 (defun xscheme-send-current-line ()
 624   "Send the current line to the Scheme process.
 625 Useful for working with debugging Scheme under adb."
 626   (interactive)
 627   (let ((line
 628          (save-excursion
 629            (beginning-of-line)
 630            (let ((start (point)))
 631              (end-of-line)
 632              (buffer-substring start (point))))))
 633     (end-of-line)
 634     (insert ?\n)
 635     (xscheme-send-string-2 line)))
 636
 637 (defun xscheme-send-buffer ()
 638   "Send the current buffer to the Scheme process."
 639   (interactive)
 640   (if (xscheme-process-buffer-current-p)
 641       (error "Not allowed to send this buffer's contents to Scheme"))
 642   (xscheme-send-region (point-min) (point-max)))
 643
 644 (defun xscheme-send-char (char)
 645   "Prompt for a character and send it to the Scheme process."
 646   (interactive "cCharacter to send: ")
 647   (process-send-string xscheme-process-name (char-to-string char)))
 648
 649 (defun xscheme-delete-output ()
 650   "Delete all output from interpreter since last input."
 651   (interactive)
 652   (let ((proc (get-buffer-process (current-buffer))))
 653     (save-excursion
 654       (goto-char (process-mark proc))
 655       (re-search-backward
 656        "^;\\(Unspecified return value$\\|Value\\( [0-9]+\\)?: \\|\\(Abort\\|Up\\|Quit\\)!$\\)"
 657        xscheme-last-input-end
 658        t)
 659       (forward-line 0)
 660       (if (< (marker-position xscheme-last-input-end) (point))
 661           (progn
 662             (delete-region xscheme-last-input-end (point))
 663             (insert-before-markers "*** output flushed ***\n"))))))
 664 \f
 665 ;;;; Interrupts
 666
 667 (defun xscheme-send-breakpoint-interrupt ()
 668   "Cause the Scheme process to enter a breakpoint."
 669   (interactive)
 670   (xscheme-send-interrupt ?b nil))
 671
 672 (defun xscheme-send-proceed ()
 673   "Cause the Scheme process to proceed from a breakpoint."
 674   (interactive)
 675   (process-send-string xscheme-process-name "(proceed)\n"))
 676
 677 (defun xscheme-send-control-g-interrupt ()
 678   "Cause the Scheme processor to halt and flush input.
 679 Control returns to the top level rep loop."
 680   (interactive)
 681   (let ((inhibit-quit t))
 682     (cond ((not xscheme-control-g-synchronization-p)
 683            (interrupt-process xscheme-process-name))
 684           ((save-excursion
 685              (set-buffer xscheme-buffer-name)
 686              xscheme-control-g-disabled-p)
 687            (message "Relax..."))
 688           (t
 689            (save-excursion
 690              (set-buffer xscheme-buffer-name)
 691              (setq xscheme-control-g-disabled-p t))
 692            (message xscheme-control-g-message-string)
 693            (interrupt-process xscheme-process-name)
 694            (sleep-for 0.1)
 695            (xscheme-send-char 0)))))
 696
 697 (defconst xscheme-control-g-message-string
 698   "Sending C-G interrupt to Scheme...")
 699
 700 (defun xscheme-send-control-u-interrupt ()
 701   "Cause the Scheme process to halt, returning to previous rep loop."
 702   (interactive)
 703   (xscheme-send-interrupt ?u t))
 704
 705 (defun xscheme-send-control-x-interrupt ()
 706   "Cause the Scheme process to halt, returning to current rep loop."
 707   (interactive)
 708   (xscheme-send-interrupt ?x t))
 709
 710 ;;; This doesn't really work right -- Scheme just gobbles the first
 711 ;;; character in the input.  There is no way for us to guarantee that
 712 ;;; the argument to this procedure is the first char unless we put
 713 ;;; some kind of marker in the input stream.
 714
 715 (defun xscheme-send-interrupt (char mark-p)
 716   "Send a ^A type interrupt to the Scheme process."
 717   (interactive "cInterrupt character to send: ")
 718   (quit-process xscheme-process-name)
 719   (sleep-for 0.1)
 720   (xscheme-send-char char)
 721   (if (and mark-p xscheme-control-g-synchronization-p)
 722       (xscheme-send-char 0)))
 723 \f
 724 ;;;; Internal Variables
 725
 726 (defvar xscheme-process-command-line nil
 727   "Command used to start the most recent Scheme process.")
 728
 729 (defvar xscheme-process-name "scheme"
 730   "Name of xscheme process that we're currently interacting with.")
 731
 732 (defvar xscheme-buffer-name "*scheme*"
 733   "Name of xscheme buffer that we're currently interacting with.")
 734
 735 (defvar xscheme-expressions-ring-max 30
 736   "*Maximum length of Scheme expressions ring.")
 737
 738 (defvar xscheme-expressions-ring nil
 739   "List of expressions recently transmitted to the Scheme process.")
 740
 741 (defvar xscheme-expressions-ring-yank-pointer nil
 742   "The tail of the Scheme expressions ring whose car is the last thing yanked.")
 743
 744 (defvar xscheme-last-input-end)
 745
 746 (defvar xscheme-process-filter-state 'idle
 747   "State of scheme process escape reader state machine:
 748 idle                   waiting for an escape sequence
 749 reading-type           received an altmode but nothing else
 750 reading-string         reading prompt string")
 751
 752 (defvar xscheme-running-p nil
 753   "This variable, if nil, indicates that the scheme process is
 754 waiting for input.  Otherwise, it is busy evaluating something.")
 755
 756 (defconst xscheme-control-g-synchronization-p t
 757   "If non-nil, insert markers in the scheme input stream to indicate when
 758 control-g interrupts were signaled.  Do not allow more control-g's to be
 759 signaled until the scheme process acknowledges receipt.")
 760
 761 (defvar xscheme-control-g-disabled-p nil
 762   "This variable, if non-nil, indicates that a control-g is being processed
 763 by the scheme process, so additional control-g's are to be ignored.")
 764
 765 (defvar xscheme-allow-output-p t
 766   "This variable, if nil, prevents output from the scheme process
 767 from being inserted into the process-buffer.")
 768
 769 (defvar xscheme-prompt ""
 770   "The current scheme prompt string.")
 771
 772 (defvar xscheme-string-accumulator ""
 773   "Accumulator for the string being received from the scheme process.")
 774
 775 (defvar xscheme-string-receiver nil
 776   "Procedure to send the string argument from the scheme process.")
 777
 778 (defconst default-xscheme-runlight
 779   '(": " xscheme-runlight-string)
 780   "Default global (shared) xscheme-runlight modeline format.")
 781
 782 (defvar xscheme-runlight "")
 783 (defvar xscheme-runlight-string nil)
 784 (defvar xscheme-mode-string nil)
 785 (setq-default scheme-mode-line-process
 786               '("" xscheme-runlight))
 787
 788 (mapcar 'make-variable-buffer-local
 789         '(xscheme-expressions-ring
 790           xscheme-expressions-ring-yank-pointer
 791           xscheme-process-filter-state
 792           xscheme-running-p
 793           xscheme-control-g-disabled-p
 794           xscheme-allow-output-p
 795           xscheme-prompt
 796           xscheme-string-accumulator
 797           xscheme-mode-string
 798           scheme-mode-line-process))
 799 \f
 800 ;;;; Basic Process Control
 801
 802 (defun xscheme-start-process (command-line the-process the-buffer)
 803   (let ((buffer (get-buffer-create the-buffer)))
 804     (let ((process (get-buffer-process buffer)))
 805       (save-excursion
 806         (set-buffer buffer)
 807         (if (and process (memq (process-status process) '(run stop)))
 808             (set-marker (process-mark process) (point-max))
 809             (progn (if process (delete-process process))
 810                    (goto-char (point-max))
 811                    (scheme-interaction-mode nil)
 812                    (setq xscheme-process-name the-process)
 813                    (if (bobp)
 814                        (insert-before-markers
 815                         (substitute-command-keys xscheme-startup-message)))
 816                    (setq process
 817                          (let ((process-connection-type nil))
 818                            (apply 'start-process
 819                                   (cons the-process
 820                                         (cons buffer
 821                                               (xscheme-parse-command-line
 822                                                command-line))))))
 823                    (if (not (equal (process-name process) the-process))
 824                        (setq xscheme-process-name (process-name process)))
 825                    (if (not (equal (buffer-name buffer) the-buffer))
 826                        (setq xscheme-buffer-name (buffer-name buffer)))
 827                    (message "Starting process %s in buffer %s"
 828                             xscheme-process-name
 829                             xscheme-buffer-name)
 830                    (set-marker (process-mark process) (point-max))
 831                    (xscheme-process-filter-initialize t)
 832                    (xscheme-modeline-initialize xscheme-buffer-name)
 833                    (set-process-sentinel process 'xscheme-process-sentinel)
 834                    (set-process-filter process 'xscheme-process-filter)
 835                    (run-hooks 'xscheme-start-hook)))))
 836     buffer))
 837
 838 (defun xscheme-parse-command-line (string)
 839   (setq string (substitute-in-file-name string))
 840   (let ((start 0)
 841         (result '()))
 842     (while start
 843       (let ((index (string-match "[ \t]" string start)))
 844         (setq start
 845               (cond ((not index)
 846                      (setq result
 847                            (cons (substring string start)
 848                                  result))
 849                      nil)
 850                     ((= index start)
 851                      (string-match "[^ \t]" string start))
 852                     (t
 853                      (setq result
 854                            (cons (substring string start index)
 855                                  result))
 856                      (1+ index))))))
 857     (nreverse result)))
 858 \f
 859 (defun xscheme-wait-for-process ()
 860   (sleep-for 2)
 861   (while xscheme-running-p
 862     (sleep-for 1)))
 863
 864 (defun xscheme-process-running-p ()
 865   "True iff there is a Scheme process whose status is `run'."
 866   (let ((process (get-process xscheme-process-name)))
 867     (and process
 868          (eq (process-status process) 'run))))
 869
 870 (defun xscheme-process-buffer ()
 871   (let ((process (get-process xscheme-process-name)))
 872     (and process (process-buffer process))))
 873
 874 (defun xscheme-process-buffer-window ()
 875   (let ((buffer (xscheme-process-buffer)))
 876     (and buffer (get-buffer-window buffer))))
 877
 878 (defun xscheme-process-buffer-current-p ()
 879   "True iff the current buffer is the Scheme process buffer."
 880   (eq (xscheme-process-buffer) (current-buffer)))
 881 \f
 882 ;;;; Process Filter
 883
 884 (defun xscheme-process-sentinel (proc reason)
 885   (let* ((buffer (process-buffer proc))
 886          (name (buffer-name buffer)))
 887     (save-excursion
 888       (set-buffer buffer)
 889       (xscheme-process-filter-initialize (eq reason 'run))
 890       (if (not (eq reason 'run))
 891           (progn
 892             (setq scheme-mode-line-process "")
 893             (setq xscheme-mode-string "no process")
 894             (if (equal name (default-value 'xscheme-buffer-name))
 895                 (setq-default xscheme-runlight ""))))
 896       (if (and (not (memq reason '(run stop)))
 897                xscheme-signal-death-message)
 898           (progn
 899             (beep)
 900             (message
 901 "The Scheme process has died!  Do M-x reset-scheme to restart it"))))))
 902
 903 (defun xscheme-process-filter-initialize (running-p)
 904   (setq xscheme-process-filter-state 'idle)
 905   (setq xscheme-running-p running-p)
 906   (setq xscheme-control-g-disabled-p nil)
 907   (setq xscheme-allow-output-p t)
 908   (setq xscheme-prompt "")
 909   (if running-p
 910       (let ((name (buffer-name (current-buffer))))
 911         (setq scheme-mode-line-process '(": " xscheme-runlight-string))
 912         (xscheme-modeline-initialize name)
 913         (if (equal name (default-value 'xscheme-buffer-name))
 914             (setq-default xscheme-runlight default-xscheme-runlight))))
 915   (if (or (eq xscheme-runlight default-xscheme-runlight)
 916           (equal xscheme-runlight ""))
 917       (setq xscheme-runlight (list ": " 'xscheme-buffer-name ": " "?")))
 918   (rplaca (nthcdr 3 xscheme-runlight)
 919           (if running-p "?" "no process")))
 920
 921 (defun xscheme-process-filter (proc string)
 922   (let ((xscheme-filter-input string)
 923         (call-noexcursion nil))
 924     (while xscheme-filter-input
 925       (setq call-noexcursion nil)
 926       (save-excursion
 927         (set-buffer (process-buffer proc))
 928         (cond ((eq xscheme-process-filter-state 'idle)
 929                (let ((start (string-match "\e" xscheme-filter-input)))
 930                  (if start
 931                      (progn
 932                        (xscheme-process-filter-output
 933                         (substring xscheme-filter-input 0 start))
 934                        (setq xscheme-filter-input
 935                              (substring xscheme-filter-input (1+ start)))
 936                        (setq xscheme-process-filter-state 'reading-type))
 937                    (let ((string xscheme-filter-input))
 938                      (setq xscheme-filter-input nil)
 939                      (xscheme-process-filter-output string)))))
 940               ((eq xscheme-process-filter-state 'reading-type)
 941                (if (zerop (length xscheme-filter-input))
 942                    (setq xscheme-filter-input nil)
 943                  (let ((char (aref xscheme-filter-input 0)))
 944                    (setq xscheme-filter-input
 945                          (substring xscheme-filter-input 1))
 946                    (let ((entry (assoc char xscheme-process-filter-alist)))
 947                      (if entry
 948                          (funcall (nth 2 entry) (nth 1 entry))
 949                        (progn
 950                          (xscheme-process-filter-output ?\e char)
 951                          (setq xscheme-process-filter-state 'idle)))))))
 952               ((eq xscheme-process-filter-state 'reading-string)
 953                (let ((start (string-match "\e" xscheme-filter-input)))
 954                  (if start
 955                      (let ((string
 956                             (concat xscheme-string-accumulator
 957                                     (substring xscheme-filter-input 0 start))))
 958                        (setq xscheme-filter-input
 959                              (substring xscheme-filter-input (1+ start)))
 960                        (setq xscheme-process-filter-state 'idle)
 961                        (if (listp xscheme-string-receiver)
 962                            (progn
 963                              (setq xscheme-string-receiver
 964                                    (car xscheme-string-receiver))
 965                              (setq call-noexcursion string))
 966                          (funcall xscheme-string-receiver string)))
 967                    (progn
 968                      (setq xscheme-string-accumulator
 969                            (concat xscheme-string-accumulator
 970                                    xscheme-filter-input))
 971                      (setq xscheme-filter-input nil)))))
 972               (t
 973                (error "Scheme process filter -- bad state"))))
 974       (if call-noexcursion
 975           (funcall xscheme-string-receiver call-noexcursion)))))
 976 \f
 977 ;;;; Process Filter Output
 978
 979 (defun xscheme-process-filter-output (&rest args)
 980   (if xscheme-allow-output-p
 981       (let ((string (apply 'concat args)))
 982         (save-excursion
 983           (xscheme-goto-output-point)
 984           (let ((old-point (point)))
 985             (while (string-match "\\(\007\\|\f\\)" string)
 986               (let ((start (match-beginning 0))
 987                     (end (match-end 0)))
 988                 (insert-before-markers (substring string 0 start))
 989                 (if (= ?\f (aref string start))
 990                     (progn
 991                       (if (not (bolp))
 992                           (insert-before-markers ?\n))
 993                       (insert-before-markers ?\f))
 994                     (beep))
 995                 (setq string (substring string (1+ start)))))
 996             (insert-before-markers string)
 997             (if (and xscheme-last-input-end
 998                      (equal (marker-position xscheme-last-input-end) (point)))
 999                 (set-marker xscheme-last-input-end old-point)))))))
1000
1001 (defun xscheme-guarantee-newlines (n)
1002   (if xscheme-allow-output-p
1003       (save-excursion
1004         (xscheme-goto-output-point)
1005         (let ((stop nil))
1006           (while (and (not stop)
1007                       (bolp))
1008             (setq n (1- n))
1009             (if (bobp)
1010                 (setq stop t)
1011                 (backward-char))))
1012         (xscheme-goto-output-point)
1013         (while (> n 0)
1014           (insert-before-markers ?\n)
1015           (setq n (1- n))))))
1016
1017 (defun xscheme-goto-output-point ()
1018   (let ((process (get-process xscheme-process-name)))
1019     (set-buffer (process-buffer process))
1020     (goto-char (process-mark process))))
1021
1022 (defun xscheme-modeline-initialize (name)
1023   (setq xscheme-runlight-string "")
1024   (if (equal name (default-value 'xscheme-buffer-name))
1025       (setq-default xscheme-runlight-string ""))
1026   (setq xscheme-mode-string "")
1027   (setq mode-line-buffer-identification
1028         (list (concat name ": ")
1029               'xscheme-mode-string)))
1030
1031 (defun xscheme-set-runlight (runlight)
1032   (setq xscheme-runlight-string runlight)
1033   (if (equal (buffer-name (current-buffer))
1034              (default-value 'xscheme-buffer-name))
1035       (setq-default xscheme-runlight-string runlight))
1036   (rplaca (nthcdr 3 xscheme-runlight) runlight)
1037   (force-mode-line-update t))
1038 \f
1039 ;;;; Process Filter Operations
1040
1041 (defvar xscheme-process-filter-alist
1042   '((?A xscheme-eval
1043         xscheme-process-filter:string-action-noexcursion)
1044     (?D xscheme-enter-debugger-mode
1045         xscheme-process-filter:string-action)
1046     (?E xscheme-eval
1047         xscheme-process-filter:string-action)
1048     (?P xscheme-set-prompt-variable
1049         xscheme-process-filter:string-action)
1050     (?R xscheme-enter-interaction-mode
1051         xscheme-process-filter:simple-action)
1052     (?b xscheme-start-gc
1053         xscheme-process-filter:simple-action)
1054     (?c xscheme-unsolicited-read-char
1055         xscheme-process-filter:simple-action)
1056     (?e xscheme-finish-gc
1057         xscheme-process-filter:simple-action)
1058     (?f xscheme-exit-input-wait
1059         xscheme-process-filter:simple-action)
1060     (?g xscheme-enable-control-g
1061         xscheme-process-filter:simple-action)
1062     (?i xscheme-prompt-for-expression
1063         xscheme-process-filter:string-action)
1064     (?m xscheme-message
1065         xscheme-process-filter:string-action)
1066     (?n xscheme-prompt-for-confirmation
1067         xscheme-process-filter:string-action)
1068     (?o xscheme-output-goto
1069         xscheme-process-filter:simple-action)
1070     (?p xscheme-set-prompt
1071         xscheme-process-filter:string-action)
1072     (?s xscheme-enter-input-wait
1073         xscheme-process-filter:simple-action)
1074     (?v xscheme-write-value
1075         xscheme-process-filter:string-action)
1076     (?w xscheme-cd
1077         xscheme-process-filter:string-action)
1078     (?z xscheme-display-process-buffer
1079         xscheme-process-filter:simple-action))
1080   "Table used to decide how to handle process filter commands.
1081 Value is a list of entries, each entry is a list of three items.
1082
1083 The first item is the character that the process filter dispatches on.
1084 The second item is the action to be taken, a function.
1085 The third item is the handler for the entry, a function.
1086
1087 When the process filter sees a command whose character matches a
1088 particular entry, it calls the handler with two arguments: the action
1089 and the string containing the rest of the process filter's input
1090 stream.  It is the responsibility of the handler to invoke the action
1091 with the appropriate arguments, and to reenter the process filter with
1092 the remaining input.")
1093 \f
1094 (defun xscheme-process-filter:simple-action (action)
1095   (setq xscheme-process-filter-state 'idle)
1096   (funcall action))
1097
1098 (defun xscheme-process-filter:string-action (action)
1099   (setq xscheme-string-receiver action)
1100   (setq xscheme-string-accumulator "")
1101   (setq xscheme-process-filter-state 'reading-string))
1102
1103 (defun xscheme-process-filter:string-action-noexcursion (action)
1104   (xscheme-process-filter:string-action (cons action nil)))
1105
1106 (defconst xscheme-runlight:running "run"
1107   "The character displayed when the Scheme process is running.")
1108
1109 (defconst xscheme-runlight:input "input"
1110   "The character displayed when the Scheme process is waiting for input.")
1111
1112 (defconst xscheme-runlight:gc "gc"
1113   "The character displayed when the Scheme process is garbage collecting.")
1114
1115 (defun xscheme-start-gc ()
1116   (xscheme-set-runlight xscheme-runlight:gc))
1117
1118 (defun xscheme-finish-gc ()
1119   (xscheme-set-runlight
1120    (if xscheme-running-p xscheme-runlight:running xscheme-runlight:input)))
1121
1122 (defun xscheme-enter-input-wait ()
1123   (xscheme-set-runlight xscheme-runlight:input)
1124   (setq xscheme-control-g-disabled-p nil)
1125   (setq xscheme-running-p nil))
1126
1127 (defun xscheme-exit-input-wait ()
1128   (xscheme-set-runlight xscheme-runlight:running)
1129   (setq xscheme-running-p t))
1130
1131 (defun xscheme-enable-control-g ()
1132   (setq xscheme-control-g-disabled-p nil)
1133   (if (string= (current-message) xscheme-control-g-message-string)
1134       (message nil)))
1135
1136 (defun xscheme-display-process-buffer ()
1137   (let ((window (or (xscheme-process-buffer-window)
1138                     (display-buffer (xscheme-process-buffer)))))
1139     (save-window-excursion
1140       (select-window window)
1141       (xscheme-goto-output-point)
1142       (if (xscheme-debugger-mode-p)
1143           (xscheme-enter-interaction-mode)))))
1144
1145 (defun xscheme-unsolicited-read-char ()
1146   nil)
1147 \f
1148 (defun xscheme-eval (string)
1149   (eval (car (read-from-string string))))
1150
1151 (defun xscheme-message (string)
1152   (if (not (zerop (length string)))
1153       (xscheme-write-message-1 string (format ";%s" string))))
1154
1155 (defun xscheme-write-value (string)
1156   (if (zerop (length string))
1157       (xscheme-write-message-1 "(no value)" ";Unspecified return value")
1158       (xscheme-write-message-1 string (format ";Value: %s" string))))
1159
1160 (defun xscheme-write-message-1 (message-string output-string)
1161   (let* ((process (get-process xscheme-process-name))
1162          (window (get-buffer-window (process-buffer process))))
1163     (if (or (not window)
1164             (not (pos-visible-in-window-p (process-mark process)
1165                                           window)))
1166         (message "%s" message-string)))
1167   (xscheme-guarantee-newlines 1)
1168   (xscheme-process-filter-output output-string))
1169
1170 (defun xscheme-set-prompt-variable (string)
1171   (setq xscheme-prompt string))
1172
1173 (defun xscheme-set-prompt (string)
1174   (setq xscheme-prompt string)
1175   (xscheme-guarantee-newlines 2)
1176   (setq xscheme-mode-string (xscheme-coerce-prompt string))
1177   (force-mode-line-update t))
1178
1179 (defun xscheme-output-goto ()
1180   (xscheme-goto-output-point)
1181   (xscheme-guarantee-newlines 2))
1182
1183 (defun xscheme-coerce-prompt (string)
1184   (if (string-match "^[0-9]+ \\[[^]]+\\] " string)
1185       (let ((end (match-end 0)))
1186         (xscheme-process-filter-output (substring string end))
1187         (substring string 0 (- end 1)))
1188       string))
1189
1190 (defun xscheme-cd (directory-string)
1191   (save-excursion
1192     (set-buffer (xscheme-process-buffer))
1193     (cd directory-string)))
1194 \f
1195 (defun xscheme-prompt-for-confirmation (prompt-string)
1196   (xscheme-send-char (if (y-or-n-p prompt-string) ?y ?n)))
1197
1198 (defun xscheme-prompt-for-expression (prompt-string)
1199   (xscheme-send-string-2
1200    (read-from-minibuffer prompt-string nil xscheme-prompt-for-expression-map)))
1201
1202 (defvar xscheme-prompt-for-expression-map nil)
1203 (if (not xscheme-prompt-for-expression-map)
1204     (progn
1205       (setq xscheme-prompt-for-expression-map
1206             (copy-keymap minibuffer-local-map))
1207       (substitute-key-definition 'exit-minibuffer
1208                                  'xscheme-prompt-for-expression-exit
1209                                  xscheme-prompt-for-expression-map)))
1210
1211 (defun xscheme-prompt-for-expression-exit ()
1212   (interactive)
1213   (if (eq (xscheme-region-expression-p (point-min) (point-max)) 'one)
1214       (exit-minibuffer)
1215       (error "input must be a single, complete expression")))
1216
1217 (defun xscheme-region-expression-p (start end)
1218   (save-excursion
1219     (let ((old-syntax-table (syntax-table)))
1220       (unwind-protect
1221           (progn
1222             (set-syntax-table scheme-mode-syntax-table)
1223             (let ((state (parse-partial-sexp start end)))
1224               (and (zerop (car state))  ;depth = 0
1225                    (nth 2 state)        ;last-sexp exists, i.e. >= 1 sexps
1226                    (let ((state (parse-partial-sexp start (nth 2 state))))
1227                      (if (nth 2 state) 'many 'one)))))
1228         (set-syntax-table old-syntax-table)))))
1229
1230 (provide 'xscheme)
1231
1232 ;;; xscheme.el ends here