From d68ccf7c2ae9516ca2ddacc5f65e2277038b23f6 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson@vistahigherlearning.com>
Date: Wed, 5 Oct 2022 10:28:37 -0400
Subject: Add Lisp lexer.

---
 syntax-highlight/lisp.scm | 100 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 syntax-highlight/lisp.scm

(limited to 'syntax-highlight/lisp.scm')

diff --git a/syntax-highlight/lisp.scm b/syntax-highlight/lisp.scm
new file mode 100644
index 0000000..88d7fba
--- /dev/null
+++ b/syntax-highlight/lisp.scm
@@ -0,0 +1,100 @@
+;;; guile-syntax-highlight --- General-purpose syntax highlighter
+;;; Copyright © 2022 David Thompson <davet@gnu.org>
+;;;
+;;; Guile-syntax-highlight is free software; you can redistribute it
+;;; and/or modify it under the terms of the GNU Lesser General Public
+;;; License as published by the Free Software Foundation; either
+;;; version 3 of the License, or (at your option) any later version.
+;;;
+;;; Guile-syntax-highlight 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 Lesser General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU Lesser General Public
+;;; License along with guile-syntax-highlight.  If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+;; Syntax highlighting for Lisp.
+;;
+;;; Code:
+
+(define-module (syntax-highlight lisp)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-26)
+  #:use-module (syntax-highlight lexers)
+  #:export (%default-special-symbols
+            %default-special-prefixes
+            make-lisp-lexer
+            lex-lisp))
+
+(define char-set:lisp-delimiters
+  (char-set-union char-set:whitespace
+                  (char-set #\( #\) #\[ #\] #\{ #\})))
+
+(define char-set:lisp-symbol
+  (char-set-complement char-set:lisp-delimiters))
+
+(define %default-special-symbols
+  '("setq" "setf"
+    "case" "ccase" "ecase"
+    "if" "cond"
+    "prog1" "prog2" "progn"
+    "lambda" "λ"
+    "let" "let*"
+    "and" "or"))
+
+(define %default-special-prefixes
+  '("def"))
+
+(define (lex-special-symbol sym)
+  (lex-filter (lambda (str)
+                (string=? sym str))
+              (lex-char-set char-set:lisp-symbol)))
+
+(define (lex-special-symbol symbols prefixes)
+  (lex-filter (lambda (str)
+                (or (any (cut string=? symbols <>) symbols)
+                    (any (cut string-prefix? <> str) prefixes)))
+              (lex-char-set char-set:lisp-symbol)))
+
+(define (lex-map2 proc lexer)
+  (lambda (tokens cursor)
+    (let-values (((result remainder) (lexer tokens cursor)))
+      (if result
+          (match (token-take result 2)
+            ((second first) ; accumulator tokens are in reverse order
+             (values (token-add (token-drop result 2)
+                                (proc first second))
+                     remainder)))
+          (fail)))))
+
+(define (make-lisp-lexer special-symbols special-prefixes)
+  "Return a lexer that highlights Lisp source code.  Tag strings
+that are in SPECIAL-SYMBOLS or match one of the string prefixes in
+SPECIAL-PREFIXES with the 'special' tag."
+  (lex-consume
+   (lex-any (lex-char-set char-set:whitespace)
+            (lex-tag 'open (lex-any* (map lex-string '("(" "[" "{"))))
+            (lex-tag 'close (lex-any* (map lex-string '(")" "]" "}"))))
+            (lex-tag 'comment (lex-delimited ";" #:until "\n"))
+            (lex-tag 'special
+                     (lex-filter (lambda (str)
+                                   (or (any (cut string=? <> str)
+                                            special-symbols)
+                                       (any (cut string-prefix? <> str)
+                                            special-prefixes)))
+                                 (lex-char-set char-set:lisp-symbol)))
+            (lex-tag 'string (lex-delimited "\""))
+            (lex-tag 'keyword
+                     (lex-map2 string-append
+                               (lex-all (lex-string ":")
+                                        (lex-char-set char-set:lisp-symbol))))
+            (lex-tag 'symbol (lex-char-set char-set:lisp-symbol)))))
+
+(define lex-lisp
+  (make-lisp-lexer %default-special-symbols %default-special-prefixes))
-- 
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