GNU bug report logs - #41353
'thunk?' documentation is misleading

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Jan Synacek <jsynacek <at> redhat.com>
To: bug-guile <at> gnu.org
Subject: (const x) is a thunk
Date: Sun, 17 May 2020 12:41:05 +0200

With guile-3.0.2:

scheme@(guile-user)> (thunk? (const 1))
$1 = #t

Since thunk is a procedure that does not accept arguments (section
6.9.7, documentation for 'thunk?'), the result of the above evaluation
should be #f.

Message #8 received at 41353 <at> debbugs.gnu.org (full text, mbox):

From: David Kastrup <dak <at> gnu.org>
To: 41353 <at> debbugs.gnu.org
Subject: (thunk? (const 1))
Date: Sun, 17 May 2020 16:08:50 +0200

I think this is more a matter of the documentation being not quite right:

 -- Scheme Procedure: thunk? obj
 -- C Function: scm_thunk_p (obj)
     Return ‘#t’ if OBJ is a thunk—a procedure that does not accept
     arguments.

"if OBJ can serve as a thunk—a procedure called without arguments."

Note that (thunk? (lambda x x)) also returns #t and that ((const 1))
returns 1.

-- 
David Kastrup

Message #11 received at 41353 <at> debbugs.gnu.org (full text, mbox):

From: Jan Synacek <jsynacek <at> redhat.com>
To: 41353 <at> debbugs.gnu.org
Subject: Re: bug#41353: (thunk? (const 1))
Date: Sun, 17 May 2020 16:46:40 +0200

On Sun, May 17, 2020 at 4:09 PM David Kastrup <dak <at> gnu.org> wrote:
> I think this is more a matter of the documentation being not quite right:
>
>  -- Scheme Procedure: thunk? obj
>  -- C Function: scm_thunk_p (obj)
>      Return ‘#t’ if OBJ is a thunk—a procedure that does not accept
>      arguments.
>
> "if OBJ can serve as a thunk—a procedure called without arguments."
>
> Note that (thunk? (lambda x x)) also returns #t and that ((const 1))
> returns 1.

But both (lambda x ...) and (const whatever) are still a procedure that accepts
an argument, aren't they? My understanding of thunk is (lambda () ...),
because that's a procedure that takes zero arguments.

Message #14 received at 41353 <at> debbugs.gnu.org (full text, mbox):

From: lloda <lloda <at> sarc.name>
To: Jan Synacek <jsynacek <at> redhat.com>
Cc: 41353 <at> debbugs.gnu.org
Subject: Re: bug#41353: (thunk? (const 1))
Date: Sun, 17 May 2020 17:31:22 +0200

> On 17 May 2020, at 16:46, Jan Synacek <jsynacek <at> redhat.com> wrote:
> 
> On Sun, May 17, 2020 at 4:09 PM David Kastrup <dak <at> gnu.org> wrote:
>> I think this is more a matter of the documentation being not quite right:
>> 
>> -- Scheme Procedure: thunk? obj
>> -- C Function: scm_thunk_p (obj)
>>     Return ‘#t’ if OBJ is a thunk—a procedure that does not accept
>>     arguments.
>> 
>> "if OBJ can serve as a thunk—a procedure called without arguments."
>> 
>> Note that (thunk? (lambda x x)) also returns #t and that ((const 1))
>> returns 1.
> 
> But both (lambda x ...) and (const whatever) are still a procedure that accepts
> an argument, aren't they? My understanding of thunk is (lambda () ...),
> because that's a procedure that takes zero arguments.

(lambda x ...) takes any number of arguments, including none.

Message #21 received at 41353-done <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: David Kastrup <dak <at> gnu.org>
Cc: 41353-done <at> debbugs.gnu.org
Subject: Re: bug#41353: (thunk? (const 1))
Date: Wed, 27 May 2020 22:50:04 +0200

Hi,

David Kastrup <dak <at> gnu.org> skribis:

> I think this is more a matter of the documentation being not quite right:
>
>  -- Scheme Procedure: thunk? obj
>  -- C Function: scm_thunk_p (obj)
>      Return ‘#t’ if OBJ is a thunk—a procedure that does not accept
>      arguments.
>
> "if OBJ can serve as a thunk—a procedure called without arguments."

Agreed.  Fixed in 9c03e44dcfc118c37d28bb948f4d255c7b755d96.

Thanks,
Ludo’.

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