> Here is a very simple macro example which shows some of the features:
> destructuring, substituting into a template to produce a form,
> using (gensym) to invent a needed symbol. The purpose of this macro
> is to introduce a very simple language feature; a loop construct
> which executes a sequence of forms N times, where N is a parameter.
> We implement our new kind of loop, which we will call ``ntimes''
> in terms of the Common LISP ``dotimes' loop:
>
> (defmacro ntimes (count . forms) (let ((counter (gensym)))
> `(dotimes
> (,counter ,count) ,@forms)))

Scheme

(define-syntax ntimes
(syntax-rules ()
[(_ count forms ...)
(do ((n 0 (+ n 1)))
((= n count))
forms ...)]))

On Thu, 4 Jul 2024 22:04:48 -0000 (UTC), B. Pym wrote:

> (define-syntax ntimes
> (syntax-rules ()
> [(_ count forms ...)
> (do ((n 0 (+ n 1)))
> ((= n count))
> forms ...)]))

I think it’s a sign of desperation when you hope that using different
kinds of bracketing symbols will somehow make your code clearer. The
screen/page is two-dimensional; why not make use of both dimensions in
laying out your code?

(define-syntax ntimes
(syntax-rules ()
((_ count forms ...)
(do ((n 0 (+ n 1)))
((= n count))
forms ...
) ; do
)
) ; syntax-rules
) ; define