Colorize unified diff output

diffc.scm

(require-extension ansi-escape-sequences)
(require-extension srfi-13)
(require-extension extras)

(define (colorize txt)
  (set-text 
   (cond 
    ((string-prefix? "---" txt) '(bold))
    ((string-prefix? "+++" txt) '(bold))
    ((string-prefix? "-" txt)   '(fg-red ))
    ((string-prefix? "+" txt)   '(fg-green))
    ((string-prefix? "@@" txt)  '(fg-cyan))
    (else '()))
  txt))

(define (colorize-lines)
  (let ((l (read-line)))
    (if  (not (eof-object? l))  
	 (begin ((compose print colorize) l)
		(colorize-lines)))))

(colorize-lines)