Using special characters in Emacs Scheme buffers (#49)

Author: arthurgleckler

recipes/display-unicode-symbols-in-emacs.md

@@ -0,0 +1,34 @@
+# Display some symbols in Scheme buffers using special characters
+
+## Problem
+
+In Emacs, one can display some keywords, like `lambda` and `>=`, using
+special characters like `λ` and `≥`.
+
+## Solution
+
+```Emacs-Lisp
+(defvar pretty-scheme-keywords
+  '(("\\(->\\)" . #x2192)
+    ("\\(<=\\)" . #x2264)
+    ("\\(<==\\)" . #x21d0)
+    ("\\(>=\\)" . #x2265)
+    ("\\(==>\\)" . #x21d2))
+  "alist from regexps to Unicode code points")
+
+(defun prettify-scheme ()
+  (add-to-list 'prettify-symbols-alist '("lambda" . ?x3bb))
+  (font-lock-add-keywords
+   nil
+   (mapcar (lambda (keyword)
+             `(,(car keyword)
+               (0 (progn (compose-region (match-beginning 1) (match-end 1)
+                                         ,(cdr keyword)
+                                         'decompose-region)
+                         nil))))
+           pretty-scheme-keywords))
+  (prettify-quotes)
+  (turn-on-font-lock))
+
+(add-hook 'scheme-mode-hook 'prettify-scheme)
+```