From: Ola Bini <ola.bini@...>
Date: 2006-07-28T04:12:28+09:00
Subject: Re: RLisp - Lisp naturally embedded in Ruby

Tomasz Wegrzanowski wrote:
> On 7/27/06, Daniel Martin <martin@snowplow.org> wrote:
>> "Tomasz Wegrzanowski" <tomasz.wegrzanowski@gmail.com> writes:
>> > Can we macro around it or something, so that
>> > (set-local-variable variable value) introduces a function-local 
>> variable
>> > without increasing indentation level each time it's being done?
>> >
>> > I think it's reasonable to write something like that (whatever the 
>> names
>> > of set-local-variable operator is):
>> >
>> > (defun veclen (x y)
>> >  (set-local-variable x2 (* x x))
>> >  (set-local-variable y2 (* y y))
>> >  (set-local-variable z2 (+ x2 y2))
>> >  (sqrt z2)
>> > )
>>
>> Well, you can't quite do that but you can easily do something like
>> this:
>>
>> (defun veclen (x y)
>>   (easy-local-progn
>>     (local x2 (* x x))
>>     (local y2 (* y y))
>>     (local z2 (+ x2 y2))
>>     (sqrt z2)
>>   )
>> )
>>
>> Or:
>>
>> (defun-with-local veclen (x y)
>>   (local x2 (* x x))
>>   (local y2 (* y y))
>>   (local z2 (+ x2 y2))
>>   (sqrt z2)
>> )
> 
> So, how would such a macro look like ?
> 

You would have to do a code-walker (with all the glory such a thing 
brings), find all places where you have local and more or less replace 
them with let and let* each time you find one.

-- 
  Ola Bini (http://ola-bini.blogspot.com)
  JvYAML, RbYAML, JRuby and Jatha contributor
  System Developer, Karolinska Institutet (http://www.ki.se)
  OLogix Consulting (http://www.ologix.com)

  "Yields falsehood when quined" yields falsehood when quined.