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From: Alan Mackenzie <acm@muc.de>
To: Philip Kaludercic <philipk@posteo.net>
Cc: "Stefan Kangas" <stefankangas@gmail.com>,
	emacs-devel@gnu.org, "Mattias Engdegård" <mattiase@acm.org>
Subject: Re: Why shouldn't we have a #if .... #else .... #endif construct in Emacs Lisp?
Date: Sat, 2 Sep 2023 19:58:01 +0000	[thread overview]
Message-ID: <ZPOTyTZoHPgnc9_8@ACM> (raw)
In-Reply-To: <87pm30e60y.fsf@posteo.net>

Hello, Philip.

On Sat, Sep 02, 2023 at 19:20:29 +0000, Philip Kaludercic wrote:
> Alan Mackenzie <acm@muc.de> writes:

> > +;; Note: `static-if' handles the version of `eval' without the &optional
> > +;; parameter LEXICAL so that it can be copied unchanged for use in older
> > +;; Emacsen.

> Is this really a concern for the version that would be added to Emacs
> itself?

The idea was that there would be just one version, and a package
maintainer could copy the 13 lines to the beginning of her package
inside something like (when (not (fboundp 'static-if)) ....), but
otherwise unchanged.

> > +(defmacro static-if (condition then-form &rest else-forms)
> > +  "A conditional compilation macro analogous to C's #if.
> > +Evaluate CONDITION at macro-expansion time.  If it is non-nil,
> > +expand the macro to THEN-FORM.  Otherwise expand it to ELSE-FORMS
> > +enclosed in a `progn' form.  ELSE-FORMS may be empty."
> > +  (declare (indent 2)
> > +           (debug (sexp sexp &rest sexp)))
> > +  (if (condition-case err
> > +          (eval condition lexical-binding)
> > +        ((wrong-number-of-arguments void-variable) (eval condition))
> > +        ((debug error) (signal (car err) (cdr err))))
> > +      then-form
> > +    (cons 'progn else-forms)))

-- 
Alan Mackenzie (Nuremberg, Germany).



  parent reply	other threads:[~2023-09-02 19:58 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-28 19:37 Why shouldn't we have a #if .... #else .... #endif construct in Emacs Lisp? Alan Mackenzie
2023-08-28 19:47 ` Ulrich Mueller
2023-08-28 20:06   ` Alan Mackenzie
2023-08-28 21:01     ` Ulrich Mueller
2023-08-28 21:46       ` Alan Mackenzie
2023-08-31  2:07         ` Richard Stallman
2023-08-31  7:50           ` Alan Mackenzie
2023-09-04  1:34             ` Richard Stallman
2023-09-04 10:50               ` Alan Mackenzie
2023-09-04 11:02                 ` tomas
2023-09-04 15:19                   ` Emanuel Berg
2023-09-04 18:57                     ` tomas
2023-09-06  0:58                   ` Richard Stallman
2023-09-06  0:58                 ` Richard Stallman
2023-09-06  7:28                   ` Andreas Schwab
2023-09-06  9:31                     ` Alan Mackenzie
2023-09-06  9:56                   ` Alan Mackenzie
2023-09-09  0:39                     ` Richard Stallman
2023-09-09 10:32                       ` Ihor Radchenko
2023-09-10  0:22                         ` Richard Stallman
2023-09-10  8:36                           ` Ihor Radchenko
2023-09-13 23:53                             ` Richard Stallman
2023-09-20 12:59                               ` Ihor Radchenko
2023-09-05  0:30           ` Why have a #if .... #else .... #endif construct in Emacs Lisp, when we could make the existing code DTRT unchanged? Richard Stallman
2023-09-05  0:41             ` Emanuel Berg
2023-09-08 17:54               ` Emanuel Berg
2023-09-05  4:37             ` tomas
2023-09-05  5:53               ` Ihor Radchenko
2023-09-05  6:28                 ` tomas
2023-09-05 11:06             ` Adam Porter
2023-09-05 11:26             ` Lynn Winebarger
2023-09-05 14:11             ` Alan Mackenzie
2023-09-08  1:01               ` Richard Stallman
2023-09-08  2:45                 ` Po Lu
2023-09-10  0:24                   ` Richard Stallman
2023-09-05  8:14         ` Why shouldn't we have a #if .... #else .... #endif construct in Emacs Lisp? Ulrich Mueller
2023-08-28 19:53 ` Emanuel Berg
2023-08-29  9:19   ` Alan Mackenzie
2023-08-29 10:36   ` João Távora
2023-08-29 11:09     ` Ihor Radchenko
2023-08-29 11:20       ` João Távora
2023-08-30 20:48         ` Sean Whitton
2023-08-30 20:59           ` João Távora
2023-09-02 23:12     ` Stefan Monnier via Emacs development discussions.
2023-09-03  0:18       ` Emanuel Berg
2023-09-03 12:27       ` João Távora
2023-08-29 12:54 ` Philip Kaludercic
2023-08-29 13:23   ` Alan Mackenzie
2023-09-02 23:09   ` Stefan Monnier via Emacs development discussions.
2023-08-29 16:28 ` LdBeth
2023-08-29 20:09 ` Stefan Kangas
2023-08-30 10:31   ` Alan Mackenzie
2023-08-30 17:36     ` Stefan Kangas
2023-08-30 18:03       ` Alan Mackenzie
2023-08-30 18:17         ` Stefan Kangas
2023-09-02 15:06           ` Alan Mackenzie
2023-09-02 15:17             ` Eli Zaretskii
2023-09-02 19:43               ` Alan Mackenzie
2023-09-03  4:42                 ` Eli Zaretskii
2023-09-03 10:48                   ` Alan Mackenzie
2023-09-03 11:02                     ` Eli Zaretskii
2023-09-03 13:24                       ` Alan Mackenzie
2023-09-02 19:20             ` Philip Kaludercic
2023-09-02 19:37               ` Stefan Kangas
2023-09-02 19:58               ` Alan Mackenzie [this message]
2023-09-04 11:12                 ` Lynn Winebarger

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