1 ;;; a68-mode.el --- Major mode for editing Algol 68 code -*- lexical-binding: t; -*-
3 ;; Copyright (C) 2011 Jose E. Marchesi
4 ;; Copyright (C) 2021 Omar Polo <op@omarpolo.com>
6 ;; Author: Jose E. Marchesi
7 ;; Omar Polo <op@omarpolo.com>
8 ;; Maintainer: Omar Polo
9 ;; URL: https://git.omarpolo.com/a68-mode
10 ;; Keywords: languages
12 ;; Package-Requires: ((emacs "24.3"))
14 ;; This file is NOT part of GNU Emacs.
16 ;; This program is free software; you can redistribute it and/or modify
17 ;; it under the terms of the GNU General Public License as published by
18 ;; the Free Software Foundation; either version 3, or (at your option)
21 ;; This program is distributed in the hope that it will be useful,
22 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
23 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
24 ;; GNU General Public License for more details.
26 ;; You should have received a copy of the GNU General Public License
27 ;; along with this program; see the file COPYING. If not, write to the
28 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
29 ;; Boston, MA 02110-1301, USA.
33 ;; A major mode for editing Algol 68 code.
35 ;; This is an improved and modernized version of the a68-mode written
36 ;; by Jose E. Marchesi. The original code was taken from
38 ;; https://github.com/lachrymology/me/blob/master/.emacs.d/extras/algol-mode.el
40 ;; TODO: support quote and dot stropping.
51 "Major mode for editing Algol68 code."
55 (defcustom a68-indent-level 3
56 "Indentation step for Algol 68."
60 (defvar a68-mode-hook '()
61 "Hook run when entering Algol68 mode.")
64 (let ((map (make-sparse-keymap)))
65 (define-key map (kbd "C-j") #'newline-and-indent)
66 (define-key map (kbd "RET") #'a68-electric-terminate-line)
68 "Keymap for Algol 68 major mode.")
70 (defconst a68-font-lock-keywords
73 (or "DECS" "PROGRAM" "CONTEXT" "USE" "FINISH" "KEEP"
75 "MODE" "OP" "PRIO" "PROC"
76 "OF" "AT" "IS" "ISNT" "EMPTY" "SKIP"
78 "CASE" "IN" "OUSE" "OUT" "ESAC"
79 "FOR" "FORALL" "FROM" "TO" "BY" "WHILE" "DO" "OD"
80 "IF" "THEN" "ELIF" "THEN" "ELSE" "FI"
81 "PAR" "BEGIN" "END" "GOTO" "EXIT"
82 "LWB" "UPB" "NOT" "ABS" "BIN" "REPR" "LENG"
83 "SHORTEN" "ODD" "SIGN" "ROUND" "ENTIER" "AND" "OR"
84 "DIV" "OVER" "MOD" "ELEM" "SHL" "SHR" "OVERAB" "DIVAB" "MODAB"
87 'font-lock-keyword-face)
91 'font-lock-constant-face)
92 ;; only valid for bold stropping
93 (cons (concat "\\<[A-Z]+\\>") 'font-lock-type-face)
95 'font-lock-variable-name-face))
96 "Highlighting expressions for Algol 68 mode.")
98 (defsubst a68-within-string ()
99 "Check if inside a string."
100 (nth 3 (syntax-ppss)))
102 (defsubst a68-within-comment ()
103 "Check if inside a comment."
104 (nth 4 (syntax-ppss)))
106 ;; Indentation rules:
108 ;; - If we are at the beginning of the buffer, or looking at some
109 ;; indent-0 content, indent to column 0.
111 ;; - If we are currently at an END, ), FI or OD, then de-indent
112 ;; relative to the previous line.
114 ;; - If we first see and "end line" before our current line,
115 ;; then we should indent our current line to the same indentation as
118 ;; - If we first see a "start line" like IF, then we need to increase
119 ;; our indentation relative to that start line.
121 ;; - If into a balanced expression, we should indent to the column
122 ;; where the start of the innermost parenthetical group.
124 ;; - If none of the above apply, then do not indent at all.
126 (defun a68-indent-line ()
127 "Indent current line as Algol 68 code."
129 (let ((case-fold-search nil))
132 (if (nth 1 (syntax-ppss)) ; Check for rule 5
133 (let ((offset (save-excursion (goto-char (+ (nth 1 (syntax-ppss)) 1))
135 (indent-line-to offset))
136 (if (or (bobp) ; Check for rule 1
137 (looking-at "^[ \t]*\\<\\(KEEP\\|FINISH\\|DECS\\|USE\\|PROGRAM\\)\\>"))
139 (let ((not-indented t)
140 (prev-indent (current-indentation))
141 (begin-indent-re "^[ \t]*\\<\\(PAR\\|BEGIN\\|KEEP\\|IF\\|DO\\|ELSE\\|ELIF\\|THEN\\)")
142 (deindent-line-re "^[ \t]*\\<\\(END\\|FI\\|OD\\|ELSE\\|ELIF\\)\\>")
143 (eqindent-line-re "^[ \t]*\\<\\(THEN\\)\\>")
144 (end-line-re "^[ \t]*\\(END\\|FI\\|OD\\)")
146 (if (looking-at eqindent-line-re)
149 (setq cur-indent (current-indentation)))
150 (if (looking-at deindent-line-re) ; Check for rule 2
154 (setq cur-indent (- (current-indentation) a68-indent-level)))
155 (when (< cur-indent 0)
156 (setq cur-indent 0)))
160 (if (looking-at end-line-re) ; Check for rule 3
162 (setq cur-indent (current-indentation))
163 (setq not-indented nil))
165 (if (looking-at begin-indent-re)
167 (setq cur-indent (+ (current-indentation) a68-indent-level))
168 (setq not-indented nil))
169 (when (bobp) ; Check for rule 5
170 (setq not-indented nil))))))))
172 (indent-line-to cur-indent)
173 ;; If we didn't see an indentation hint, then allow no
175 (indent-line-to 0)))))))
176 (when (< (current-column) (current-indentation))
177 (move-to-column (current-indentation))))
179 (defvar a68-mode-syntax-table
180 (let ((st (make-syntax-table)))
181 (modify-syntax-entry ?# "<" st)
182 (modify-syntax-entry ?# ">" st)
183 (modify-syntax-entry ?\\ "." st)
184 ;; define parentheses to match
185 (modify-syntax-entry ?\( "()" st)
186 (modify-syntax-entry ?\) ")(" st)
189 (defconst a68-autoindent-lines-re
191 (or "BEGIN" "END" "ELSE" "ELIF" "DO" "OD" "CASE" "ESAC" "IN" "OUT")
194 (defun a68-electric-terminate-line ()
195 "Terminate line and indent next line."
197 ;; First, check if current line should be indented
200 (skip-chars-forward " \t")
201 (when (looking-at a68-autoindent-lines-re)
203 (delete-horizontal-space) ; Removes triling whitespaces
205 ;; Indent next line if we are not in a string
206 (unless (a68-within-string)
209 (defvar a68-mode-abbrev-table nil
210 "Abbreviation table used in `a68-mode' buffers.")
212 (define-abbrev-table 'a68-mode-abbrev-table
216 (define-derived-mode a68-mode prog-mode "Algol68"
217 "Major mode for editing Alogl68 files."
218 :abbrev-table a68-mode-abbrev-table
219 (setq-local font-lock-defaults '(a68-font-lock-keywords))
220 (setq-local indent-line-function #'a68-indent-line)
221 (setq-local comment-start "#")
222 (setq-local comment-end "#"))
225 (add-to-list 'auto-mode-alist '("\\.a68\\'" . a68-mode))
228 ;;; a68-mode.el ends here