From: Tomasz Wegrzanowski <tomasz.wegrzanowski@...>
Date: 2006-07-27T21:36:28+09:00
Subject: Re: RLisp - Lisp naturally embedded in Ruby

On 7/27/06, Christian Neukirchen <chneukirchen@gmail.com> wrote:
> > Yeah, but setf changes variables in outside scope.
> > (setf a 2)
> > (defun foo ()
> >  (setf a 3)
> >  a
> > )
> > (foo) ; -> 3
> > a ; -> 3
>
> No, that's just because a is global here.  Shadow it by a local variable:
>
> (defun foo ()
>   (let (a)
>   (setf a 3)
>   a))
>
> a     ; => 2
> (foo) ; => 3
> a     ; => 2
>
> > I think it would be a huge win if variables were local to
> > the nearest lambda (or equivalent) by default, just like in Ruby.
>
> That's why one uses LET for local variables.  ;-)

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)
)