icon.el

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;; Note: use
;;  (autoload 'icon-mode "icon" nil t)
;;  (setq auto-mode-alist (cons '("\\.icn$" . icon-mode) auto-mode-alist))
;; if not permanently installed in your emacs

;; Icon code editing commands for Emacs
;; from c-mode.el  13-Apr-88  Chris Smith;  bugs to convex!csmith
;; Copyright (C) 1988 Free Software Foundation, Inc.

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 1, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.


(defvar icon-mode-abbrev-table nil
  "Abbrev table in use in Icon-mode buffers.")
(define-abbrev-table 'icon-mode-abbrev-table ())

(defvar icon-mode-map ()
  "Keymap used in Icon mode.")
(if icon-mode-map
    ()
  (setq icon-mode-map (make-sparse-keymap))
  (define-key icon-mode-map "{" 'electric-icon-brace)
  (define-key icon-mode-map "}" 'electric-icon-brace)
  (define-key icon-mode-map "\e\C-h" 'mark-icon-function)
  (define-key icon-mode-map "\e\C-a" 'beginning-of-icon-defun)
  (define-key icon-mode-map "\e\C-e" 'end-of-icon-defun)
  (define-key icon-mode-map "\e\C-q" 'indent-icon-exp)
  (define-key icon-mode-map "\177" 'backward-delete-char-untabify)
  (define-key icon-mode-map "\t" 'icon-indent-command))

(defvar icon-mode-syntax-table nil
  "Syntax table in use in Icon-mode buffers.")

(if icon-mode-syntax-table
    ()
  (setq icon-mode-syntax-table (make-syntax-table))
  (modify-syntax-entry ?\\ "\\" icon-mode-syntax-table)
  (modify-syntax-entry ?# "<" icon-mode-syntax-table)
  (modify-syntax-entry ?\n ">" icon-mode-syntax-table)
  (modify-syntax-entry ?$ "." icon-mode-syntax-table)
  (modify-syntax-entry ?/ "." icon-mode-syntax-table)
  (modify-syntax-entry ?* "." icon-mode-syntax-table)
  (modify-syntax-entry ?+ "." icon-mode-syntax-table)
  (modify-syntax-entry ?- "." icon-mode-syntax-table)
  (modify-syntax-entry ?= "." icon-mode-syntax-table)
  (modify-syntax-entry ?% "." icon-mode-syntax-table)
  (modify-syntax-entry ?< "." icon-mode-syntax-table)
  (modify-syntax-entry ?> "." icon-mode-syntax-table)
  (modify-syntax-entry ?& "." icon-mode-syntax-table)
  (modify-syntax-entry ?| "." icon-mode-syntax-table)
  (modify-syntax-entry ?\' "\"" icon-mode-syntax-table))

(defconst icon-indent-level 4
  "*Indentation of Icon statements with respect to containing block.")
(defconst icon-brace-imaginary-offset 0
  "*Imagined indentation of a Icon open brace that actually follows a statement.")
(defconst icon-brace-offset 0
  "*Extra indentation for braces, compared with other text in same context.")
(defconst icon-continued-statement-offset 4
  "*Extra indent for lines not starting new statements.")
(defconst icon-continued-brace-offset 0
  "*Extra indent for substatements that start with open-braces.
This is in addition to icon-continued-statement-offset.")

(defconst icon-auto-newline nil
  "*Non-nil means automatically newline before and after braces,
and after colons and semicolons, inserted in C code.")

(defconst icon-tab-always-indent t
  "*Non-nil means TAB in Icon mode should always reindent the current line,
regardless of where in the line point is when the TAB command is used.")

(defun icon-mode ()
  "Major mode for editing Icon code.
Expression and list commands understand all Icon brackets.
Tab indents for Icon code.
Paragraphs are separated by blank lines only.
Delete converts tabs to spaces as it moves back.
\\{icon-mode-map}
Variables controlling indentation style:
 icon-tab-always-indent
    Non-nil means TAB in Icon mode should always reindent the current line,
    regardless of where in the line point is when the TAB command is used.
 icon-auto-newline
    Non-nil means automatically newline before and after braces
    inserted in Icon code.
 icon-indent-level
    Indentation of Icon statements within surrounding block.
    The surrounding block's indentation is the indentation
    of the line on which the open-brace appears.
 icon-continued-statement-offset
    Extra indentation given to a substatement, such as the
    then-clause of an if or body of a while.
 icon-continued-brace-offset
    Extra indentation given to a brace that starts a substatement.
    This is in addition to icon-continued-statement-offset.
 icon-brace-offset
    Extra indentation for line if it starts with an open brace.
 icon-brace-imaginary-offset
    An open brace following other text is treated as if it were
    this far to the right of the start of its line.

Turning on Icon mode calls the value of the variable icon-mode-hook with no args,
if that value is non-nil."
  (interactive)
  (kill-all-local-variables)
  (use-local-map icon-mode-map)
  (setq major-mode 'icon-mode)
  (setq mode-name "Icon")
  (setq local-abbrev-table icon-mode-abbrev-table)
  (set-syntax-table icon-mode-syntax-table)
  (make-local-variable 'paragraph-start)
  (setq paragraph-start (concat "^$\\|" page-delimiter))
  (make-local-variable 'paragraph-separate)
  (setq paragraph-separate paragraph-start)
  (make-local-variable 'indent-line-function)
  (setq indent-line-function 'icon-indent-line)
  (make-local-variable 'require-final-newline)
  (setq require-final-newline t)
  (make-local-variable 'comment-start)
  (setq comment-start "# ")
  (make-local-variable 'comment-end)
  (setq comment-end "")
  (make-local-variable 'comment-column)
  (setq comment-column 32)
  (make-local-variable 'comment-start-skip)
  (setq comment-start-skip "# *")
  (make-local-variable 'comment-indent-hook)
  (setq comment-indent-hook 'icon-comment-indent)
  (run-hooks 'icon-mode-hook))

;; This is used by indent-for-comment
;; to decide how much to indent a comment in Icon code
;; based on its context.
(defun icon-comment-indent ()
  (if (looking-at "^#")
      0				;Existing comment at bol stays there.
    (save-excursion
      (skip-chars-backward " \t")
      (max (1+ (current-column))	;Else indent at comment column
	   comment-column))))	; except leave at least one space.

(defun electric-icon-brace (arg)
  "Insert character and correct line's indentation."
  (interactive "P")
  (let (insertpos)
    (if (and (not arg)
	     (eolp)
	     (or (save-excursion
		   (skip-chars-backward " \t")
		   (bolp))
		 (if icon-auto-newline
		     (progn (icon-indent-line) (newline) t)
		   nil)))
	(progn
	  (insert last-command-char)
	  (icon-indent-line)
	  (if icon-auto-newline
	      (progn
		(newline)
		;; (newline) may have done auto-fill
		(setq insertpos (- (point) 2))
		(icon-indent-line)))
	  (save-excursion
	    (if insertpos (goto-char (1+ insertpos)))
	    (delete-char -1))))
    (if insertpos
	(save-excursion
	  (goto-char insertpos)
	  (self-insert-command (prefix-numeric-value arg)))
      (self-insert-command (prefix-numeric-value arg)))))

(defun icon-indent-command (&optional whole-exp)
  (interactive "P")
  "Indent current line as Icon code, or in some cases insert a tab character.
If icon-tab-always-indent is non-nil (the default), always indent current line.
Otherwise, indent the current line only if point is at the left margin
or in the line's indentation; otherwise insert a tab.

A numeric argument, regardless of its value,
means indent rigidly all the lines of the expression starting after point
so that this line becomes properly indented.
The relative indentation among the lines of the expression are preserved."
  (if whole-exp
      ;; If arg, always indent this line as Icon
      ;; and shift remaining lines of expression the same amount.
      (let ((shift-amt (icon-indent-line))
	    beg end)
	(save-excursion
	  (if icon-tab-always-indent
	      (beginning-of-line))
	  (setq beg (point))
	  (forward-sexp 1)
	  (setq end (point))
	  (goto-char beg)
	  (forward-line 1)
	  (setq beg (point)))
	(if (> end beg)
	    (indent-code-rigidly beg end shift-amt "#")))
    (if (and (not icon-tab-always-indent)
	     (save-excursion
	       (skip-chars-backward " \t")
	       (not (bolp))))
	(insert-tab)
      (icon-indent-line))))

(defun icon-indent-line ()
  "Indent current line as Icon code.
Return the amount the indentation changed by."
  (let ((indent (calculate-icon-indent nil))
	beg shift-amt
	(case-fold-search nil)
	(pos (- (point-max) (point))))
    (beginning-of-line)
    (setq beg (point))
    (cond ((eq indent nil)
	   (setq indent (current-indentation)))
	  ((eq indent t)
	   (setq indent (calculate-icon-indent-within-comment)))
	  ((looking-at "[ \t]*#")
	   (setq indent 0))
	  (t
	   (skip-chars-forward " \t")
	   (if (listp indent) (setq indent (car indent)))
	   (cond ((and (looking-at "else\\b")
		       (not (looking-at "else\\s_")))
		  (setq indent (save-excursion
				 (icon-backward-to-start-of-if)
				 (current-indentation))))
		 ((or (= (following-char) ?})
		      (looking-at "end\\b"))
		  (setq indent (- indent icon-indent-level)))
		 ((= (following-char) ?{)
		  (setq indent (+ indent icon-brace-offset))))))
    (skip-chars-forward " \t")
    (setq shift-amt (- indent (current-column)))
    (if (zerop shift-amt)
	(if (> (- (point-max) pos) (point))
	    (goto-char (- (point-max) pos)))
      (delete-region beg (point))
      (indent-to indent)
      ;; If initial point was within line's indentation,
      ;; position after the indentation.  Else stay at same point in text.
      (if (> (- (point-max) pos) (point))
	  (goto-char (- (point-max) pos))))
    shift-amt))

(defun calculate-icon-indent (&optional parse-start)
  "Return appropriate indentation for current line as Icon code.
In usual case returns an integer: the column to indent to.
Returns nil if line starts inside a string, t if in a comment."
  (save-excursion