GNU bug report logs - #32284
special form documentation

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

From: Nicholas Drozd <nicholasdrozd <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: special form documentation
Date: Thu, 26 Jul 2018 17:44:17 -0500

[Message part 1 (text/plain, inline)]

The Elisp manual section on Special Forms (10.2.7) lists around two dozen
special forms, but two of them aren't special forms.

* `lambda', it turns out, is not a special form, but a macro that wraps
itself in a call to the special form `function'. (The documentation for
`lambda' refers to it as "self-quoting"; this might be better changed to
"self-evaluating".)

* `track-mouse' isn't a special form, but a macro wrapper around the
primitive function `internal--track-mouse', which isn't a special form
either. (Section 29.15 on Mouse Tracking also inaccruately refers to
`track-mouse' as a special form.)

On the other hand, the special form `inline' is not listed in the Special
Forms section.

A list of all special forms can be gotten with

(let (special-forms)
  (mapatoms
   (lambda (sym)
     (when (special-form-p sym)
       (push sym special-forms))))
  (sort special-forms #'string<))

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Message #8 received at 32284 <at> debbugs.gnu.org (full text, mbox):

From: Brett Gilio <brettg <at> posteo.net>
To: Nicholas Drozd <nicholasdrozd <at> gmail.com>
Cc: 32284 <at> debbugs.gnu.org
Subject: Re: bug#32284: special form documentation
Date: Thu, 26 Jul 2018 19:04:32 -0500

Nicholas Drozd writes:

> The Elisp manual section on Special Forms (10.2.7) lists around 
> two dozen
> special forms, but two of them aren't special forms.
>
> * `lambda', it turns out, is not a special form, but a macro 
> that wraps
> itself in a call to the special form `function'. (The 
> documentation for
> `lambda' refers to it as "self-quoting"; this might be better 
> changed to
> "self-evaluating".)
>
> * `track-mouse' isn't a special form, but a macro wrapper around 
> the
> primitive function `internal--track-mouse', which isn't a 
> special form
> either. (Section 29.15 on Mouse Tracking also inaccruately 
> refers to
> `track-mouse' as a special form.)
>
> On the other hand, the special form `inline' is not listed in 
> the Special
> Forms section.
>
> A list of all special forms can be gotten with
>
> (let (special-forms)
>   (mapatoms
>    (lambda (sym)
>      (when (special-form-p sym)
>        (push sym special-forms))))
>   (sort special-forms #'string<))

Hi Nicholas,

Thank you for the note. As far as I can see you are correct about 
the
method of implementation being macros. But that does not exclude 
them
from being special forms, as from my knowledge a special form is 
simply
an expression that does not follow the formal rules for the
implementation of a function.

Most lisps define their special forms from a small subset of 
primitives
such as lambda and macros, of which these apply.

Anybody else have any input?


-- 
Brett M. Gilio
Free Software Foundation, Member
https://parabola.nu | https://emacs.org

Message #13 received at 32284-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Brett Gilio <brettg <at> posteo.net>
Cc: 32284-done <at> debbugs.gnu.org, nicholasdrozd <at> gmail.com
Subject: Re: bug#32284: special form documentation
Date: Sat, 28 Jul 2018 10:26:43 +0300

> From: Brett Gilio <brettg <at> posteo.net>
> Date: Thu, 26 Jul 2018 19:04:32 -0500
> Cc: 32284 <at> debbugs.gnu.org
> 
> Anybody else have any input?

I do: the point about track-mouse is correct: it used to be a special
form (implemented in C), but nowadays is a macro.  So I removed it
from the list of special forms.

I didn't do anything about 'lambda', because its user-facing behavior
is that of a special form, and the fact that it is a thin wrapper
around 'function' is an implementation detail that doesn't necessarily
matter in this context.

With that, I'm closing this bug report.

Thanks.

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