From: Tomasz Wegrzanowski <tomasz.wegrzanowski@...>
Date: 2006-07-28T05:50:39+09:00
Subject: Re: RLisp - Lisp naturally embedded in Ruby

On 7/27/06, Daniel Martin <martin@snowplow.org> wrote:
> "Tomasz Wegrzanowski" <tomasz.wegrzanowski@gmail.com> writes:
>
> > So, how would such a macro look like ?
>
> Well, 1) This is ruby-talk, not comp.lang.lisp, and 2) I don't
> actually know lisp.
>
> But how hard can it be, right? .... (1.5 hours later) ....
>
> Okay, try this:
>
> (defun local-expander (bodylist)
>   (cond ((null bodylist) '())
>         ((and (consp (car bodylist)) (eq (caar bodylist) 'local))
>          `((let ,(loop for x on (cdar bodylist)
>                    by #'cddr
>                    collect (list (car x) (cadr x)))
>              ,@(local-expander (cdr bodylist)))))
>         (t (cons (car bodylist) (local-expander (cdr bodylist))))))
>
> (defmacro progn-with-local (&rest body)
>   `(progn ,@(local-expander body)))
>
> (defmacro defun-with-local (name args &rest body)
>   `(defun ,name ,args ,@(local-expander body)))
>
> Then, you can do:
>
> (defun-with-local pythag (x y)
>   (local x2 (* x x))
>   (local y2 (* y y))
>   (local z2 (+ x2 y2))
>   (sqrt z2))

Wow, I'm genuinely impressed by this macro.
Now I'll try to understand it ... :-D

-- 
Tomasz Wegrzanowski [ http://t-a-w.blogspot.com/ ]