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Re: Repeat syntax

From: Alex Vong
Subject: Re: Repeat syntax
Date: Sat, 25 Nov 2017 16:39:13 +0800
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux)

Christopher Howard <address@hidden> writes:

> Hi list, I want to have a function
>   (repeat n exp exp* ...)
> That calls the expressions n times for side effect, like for-each, but
> without the bother of dealing with a list. It seems like somebody else
> must have thought of this before, but I couldn't find the equivalent
> procedure. After reading 6.10.2 I came up with this
> (define-syntax repeat
>   (syntax-rules (repeat)
>     ((_ n exp exp* ...)
>      '(unless (<= n 0)
>        exp
>        exp*
>        ...
>        (repeat (- n 1) exp exp* ...)))))
> Which doesn't work I think because repeat gets expanded infinitely many
> times. I was pondering other ways to do this, but they all seem to end
> in either infinite expansion, or an important variable getting
> overshadowed. So, could somebody point me in the right direction?

Do you want to evaluate the expressions during macro-expand-time or

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