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Re: Should letrec via syntax work within eval-when (expand load eval)?

From: Rob Browning
Subject: Re: Should letrec via syntax work within eval-when (expand load eval)?
Date: Mon, 05 Aug 2019 20:33:37 -0500

Mark H Weaver <address@hidden> writes:

> The 'letrec' form above is indeed invalid.  As the R5RS states:
>      One restriction on 'letrec' is very important: it must be possible
>      to evaluate each <init> without assigning or referring to the value
>      of any <variable>.  If this restriction is violated, then it is an
>      error.  The restriction is necessary because Scheme passes
>      arguments by value rather than by name.  In the most common uses of
>      'letrec', all the <init>s are lambda expressions and the
>      restriction is satisfied automatically.

Yeah, I'd read that originally, but not paid quite close enough
attention (obviously).  Switching to a wrapper lambda worked just fine.

> This particular example happens to work when compiled by recent versions
> of Guile, but that's suboptimal.  Ideally, we should report an error in
> this case.

Indeed, not strictly necessary, but would have been nice, so I'd have
realized more quicly that I was doing it wrong.

Thanks again for the help.
Rob Browning
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