GNU bug report logs - #17474
Making *unspecified* equivalent to (values) would seem convenient

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Message #29 received at 17474 <at> debbugs.gnu.org (full text, mbox):

From: David Kastrup <dak <at> gnu.org>
To: Mark H Weaver <mhw <at> netris.org>
Cc: 17474 <at> debbugs.gnu.org
Subject: Re: bug#17474: Another point
Date: Sun, 22 Jun 2014 07:45:04 +0200

Mark H Weaver <mhw <at> netris.org> writes:

> David Kastrup <dak <at> gnu.org> writes:
>
>> It is worth pointing out that the current state of Guile is inconsistent
>> regarding the return value of control structures: one primitive control
>> structure builder is call/cc, and its normal use does not return
>> *unspecified* but (values):
>>
>> scheme@(guile-user)> (call-with-values (lambda () (call/cc (lambda
>> (exit) (exit)))) list)
>> $5 = ()
>
> The values returned are the arguments passed to 'exit'.  Normal use is
> to pass the desired return value(s) to 'exit'.

Well, that's the point.  You'll not see anybody using a particular value
like *unspecified* for his control structures built from Scheme
primitives, and yet the C API recommends returning SCM_UNSPECIFIED.

-- 
David Kastrup

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