From cba504b509cd59f376063f6e590362b197147a2c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@lysator.liu.se>
Date: Sun, 3 Jul 2022 12:36:35 +0200
Subject: Major work.

---
 module/c/trigraph.scm | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 module/c/trigraph.scm

(limited to 'module/c/trigraph.scm')

diff --git a/module/c/trigraph.scm b/module/c/trigraph.scm
new file mode 100644
index 00000000..197e01a4
--- /dev/null
+++ b/module/c/trigraph.scm
@@ -0,0 +1,24 @@
+(define-module (c trigraph)
+  :use-module (ice-9 regex)
+  :export (replace-trigraphs))
+
+(define rx (make-regexp "\\?\\?([=\\(\\)'!<>/-])"))
+
+(define (proc m)
+  (case (string-ref (match:substring m 2) 0)
+    ((#\=) "#")
+    ((#\() "[")
+    ((#\)) "]")
+    ((#\') "^")
+    ((#\<) "{")
+    ((#\>) "}")
+    ((#\!) "|")
+    ((#\-) "~")
+    ((#\/) "\\")))
+
+(define (replace-trigraphs string)
+  (call-with-output-string
+    (lambda (port)
+      (regexp-substitute/global
+       port rx string
+       'pre proc 'post))))
-- 
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