Re: function pointer question

From	Ben Bacarisse <ben@bsb.me.uk>
Newsgroups	comp.lang.c
Subject	Re: function pointer question
Date	2026-01-03 03:33 +0000
Organization	A noiseless patient Spider
Message-ID	<87ms2v8j4t.fsf@bsb.me.uk> (permalink)
References	<10j7rs6$7c9e$1@dont-email.me> <878qeguw0p.fsf@example.invalid> <10j8liu$fgsk$2@dont-email.me> <10j8r9n$ha1t$1@dont-email.me>

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highcrew <high.crew3868@fastmail.com> writes:

> On 1/2/26 3:43 PM, Michael Sanders wrote:
>> (It's also common to define a typedef for a
>> pointer-to-function type, but I prefer to typedef the function type
>> itself
>
> OK, that's crazy! I didn't know of this!
>
> It seems a bit weird at first, but I like the type consistency:
> you declare `typedef int callback(int)` and declare `callback *c`
> making it very explicit that we are talking of a pointer.
>
> On the other hand it is not clear what `callback c` should do,
> but it makes sense as soon as you declare it.

Declarations using the function type do often make sense.  Note
"declarations" -- you can't use the typedef'd name to /define/ a function
of the given type.

A pattern I've used more than once when setting up a table of function
pointers that act like op-codes.  Maybe you have an add function, a sub
function, a mul functions and a div function.  These are all defined in
a file arithmetic.c, but the table (maybe in another file) needs to see
declarations of the names:

typedef double operation(double, double);
/* ... */

extern operation add, sub, mul, div;

static struct {
    char *name;
    operation *function;
} ops[] = {
    { "add",      add },
    { "subtract", sub },
    { "multiply", mul },
    { "divide",   div } 
};

-- 
Ben.

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function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 07:24 +0000
  Re: function pointer question Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-01-02 09:04 +0000
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 14:42 +0000
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 14:45 +0000
  Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-02 02:52 -0800
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 14:43 +0000
      Re: function pointer question highcrew <high.crew3868@fastmail.com> - 2026-01-02 17:21 +0100
        Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-02 09:37 -0800
        Re: function pointer question Ben Bacarisse <ben@bsb.me.uk> - 2026-01-03 03:33 +0000
          Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-03 07:41 -0800
            Re: function pointer question Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-01-03 21:46 +0000
              Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-04 12:03 +0100
            Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-06 20:41 +0000
              Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-07 07:18 -0800
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 21:52 -0800
                Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-08 09:17 +0100
  Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-02 17:48 +0000
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 19:35 +0000
      Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-02 12:07 -0800
        Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-03 06:06 +0000
      Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-02 21:50 +0000
      Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-02 21:52 +0000
        Re: function pointer question "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-01-02 14:18 -0800
          Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-03 13:55 +0100
            Re: function pointer question "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-01-03 12:04 -0800
              Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-03 13:01 -0800
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 07:35 -0800
                Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-07 08:17 -0800
                Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-07 08:23 -0800
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 18:44 -0800
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 18:27 -0800
              Re: function pointer question Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-01-03 22:05 +0000
            Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-03 16:39 -0800
              Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-04 12:15 +0100
            Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-06 20:33 +0000
              Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-06 17:01 -0800
        Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-03 06:08 +0000
          Re: function pointer question "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-01-05 12:40 -0800
            Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 04:30 +0000
              Re: function pointer question "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-01-06 17:05 -0800
      Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-03 17:20 -0500
        Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-03 16:48 -0800
        Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-05 08:39 +0000
          Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 12:32 +0000
            Re: function pointer question highcrew <high.crew3868@fastmail.com> - 2026-01-06 13:59 +0100
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 13:57 +0000
              Re: function pointer question antispam@fricas.org (Waldek Hebisch) - 2026-01-06 14:50 +0000
                Re: function pointer question highcrew <high.crew3868@fastmail.com> - 2026-01-06 21:44 +0100
                Re: function pointer question scott@slp53.sl.home (Scott Lurndal) - 2026-01-06 22:08 +0000
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 05:59 -0800
                Re: function pointer question antispam@fricas.org (Waldek Hebisch) - 2026-01-07 09:25 +0000
                Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-07 11:37 +0100
            Re: function pointer question Michael S <already5chosen@yahoo.com> - 2026-01-06 15:47 +0200
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 14:01 +0000
            Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-06 15:55 +0100
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 16:44 +0000
            Re: function pointer question scott@slp53.sl.home (Scott Lurndal) - 2026-01-06 15:41 +0000
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 16:45 +0000
            Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-06 10:58 -0500
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 16:49 +0000
                Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-06 12:09 -0500
                Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-07 21:18 +0000
              Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-09 09:14 -0800
              Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-10 19:17 -0800
                Re: function pointer question "James Russell Kuyper Jr." <jameskuyper@alumni.caltech.edu> - 2026-01-10 22:39 -0500
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-11 11:49 -0800
        Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-05 06:47 -0500
  Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-02 14:03 -0500
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 19:41 +0000
  Re: function pointer question bart <bc@freeuk.com> - 2026-01-02 19:18 +0000
    Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-02 11:43 -0800
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 19:44 +0000

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