Re: Repeat syntax

[Christopher Howard <christopher.howard@qlfiles.net>]

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On Sat, 2017-11-25 at 07:06 -0800, Matt Wette wrote:
> > On Nov 25, 2017, at 6:47 AM, Matt Wette <matt.wette@gmail.com>
> > wrote:
> > 
> > you probably want named let
> > 
> > ((_ n exp exp* ...)
> > (let loop ((n n))
> >     (unless (<= n 0)
> >        exp exp* ...
> >        (loop (1- n)))
> 
> but not a broken one
> 
> ((_ n exp exp* ...)
>  (let loop ((cnt n))
>    (unless (<= cnt 0)
>       exp exp* ...
>       (loop (1- cnt)))))
> 

I want both the looping and the expression evaluation to be happening
at run time. The target is to repeat the side effects of the
expressions n times, and the return values are irrelevant.

I think this last submission from Matt does exactly what I want, the
full version being

(define-syntax repeat
  (syntax-rules ()
    ((_ n exp exp* ...)
     (let loop ((cnt n))
       (unless (<= cnt 0)
         exp exp* ...
         (loop (1- cnt)))))))

scheme@(guile-user)>  (repeat 10 (display "la\n"))
la
la
la
la
la
la
la
la
la
la

The part that confuses me a little is why

(repeat 10 (display cnt))

doesn't break it. Must be that magical hygiene mentioned in the info page.

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