debug-print.lisp

;;; ref. http://practical-scheme.net/gauche/man/gauche-refj_16.html#SEC18

(defmacro debug-print (form stream)
  `(progn
     (format t "~&#?=~S:~S:~S~%"
       ,(or *load-pathname*
            (when (buffer-stream-p stream)
              (buffer-name (buffer-stream-buffer stream)))
            stream)
       ,(si:*stream-line-number stream)
       ',form)
     (let ((#1=#:values (multiple-value-list ,form)))
       (format t "~&#?-    ~{~S~%~^#?+    ~}" #1#)
       (values-list #1#))))

(set-dispatch-macro-character #\# #\?
  #'(lambda (s c n)
      (declare (ignore c n))
      (read-char s t)
      `(debug-print ,(read s t nil t) ,s)))

form が何か出力した時のために #?=... と #?- の前で fresh-line しておいた。

(progn #?=(progn (print "foo") (values 'a 'b 'c)))
#?="*scratch*":43:(progn (print "foo") (values 'a 'b 'c))

"foo" 
#?-    a
#?+    b
#?+    c
=> a
=> b
=> c