Comments on: Porting Perl’s qq to Common Lisp

By: budden

budden — Fri, 03 Apr 2009 10:39:05 +0000

Hi Leslie!
What about
http://paste.lisp.org/display/77963
This way, you won’t mislead emacs.

By: Dan Bensen

Dan Bensen — Tue, 17 Feb 2009 18:55:16 +0000

If you don’t want to deal with variable capture, you can always specify the variable’s name:

  (defmacro if-let (var test then else)
    `(let ((,var ,test))
       (if ,var
         ,then
         ,else)))

Nice code, Leslie. It’s good to see Lisp stealing useful features from other languages :)

By: Leslie

Leslie — Wed, 09 Jul 2008 07:35:31 +0000

A small change in the parser, the definition of the balanced characters. I also took the liberty of using anaphoric if.

(defparameter *balanced-chars* '((#\( . #\))
                                 (#\[ . #\])
                                 (#\{ . #\})))
 
(defmacro aif (test then else)
  `(let ((it ,test))
     (if it
       ,then
       ,else)))
 
(defun |#q-reader| (stream sub-char numarg)
  (declare (ignore sub-char numarg))
  (let* ((terminator (read-char stream))
         (terminator (aif (assoc terminator *balanced-chars*)
                          (cdr it)
                          terminator)))
    (loop for ch = (read-char stream)
          until (eql ch terminator)
          collect ch into chars
          finally (return (coerce chars 'string)))))
 
(set-dispatch-macro-character
    #\# #\q #'|#q-reader|)

By: Jarkko Hietaniemi

Jarkko Hietaniemi — Wed, 09 Jul 2008 03:23:15 +0000

How much more trickery would be needed to allow also for balanced delimiters?

qq()
qq[]
qq{}
qq

By: Leslie

Leslie — Tue, 08 Jul 2008 12:55:11 +0000

That’s nice. I know about CL-INTERPOL, but I thought it just interpolates strings via its read macro.

By: Ryan Davis

Ryan Davis — Tue, 08 Jul 2008 12:39:34 +0000

CL-INTERPOL (http://www.weitz.de/cl-interpol/) is a library for string interpolation, and has this flexible quoting you lay out here.