From: porkchop@invalid.foo
On Fri, 02 Jan 2026 02:52:22 -0800, Keith Thompson wrote:
> Michael Sanders writes:
>> i have:
>>
>> void moo(char HISTORY[][64], int hst_len, int invalid, const char *gme_msg)
>>
>> void mastermind(char HISTORY[][64], int hst_len, int invalid, const char
*gme_msg)
>>
>> to use either i have:
>>
>> void (*render)(char [][64], int, int, const char *) = MOO ? moo :
mastermind;
>>
>> my multi-part question:
>>
>> why is void required for the function pointer?
>
> Every function has a type. Every function pointer has a type. For a
> function pointer to point to a function, it must have type "pointer to
> blah", where "blah" is the type of the function.
>
> A function type includes information about the type of the function's
> result and the types of its parameters. The type of both foo and
> mastermind can be written as:
>
> void(char[]64], int, int, const char*)
>
>> A: because both moo() & mastermind return void?
>
> Yes.
>
>> B: because every function must have a return type
>> *including function pointers*?
>
> Functions and function pointers are of course distinct. A function is
> of function type. A function pointer is of an object type, specifically
> a pointer-to-function type.
>
> Every pointer-to-function type is derived from a function type, and that
> function type specifies the type returned by the function -- "void" in
> this case.
>
>> C: what about tyedef?
>
> What about it?
>
> You can define a typedef for the function type, which could make the
> code a bit simpler. (It's also common to define a typedef for a
> pointer-to-function type, but I prefer to typedef the function type
> itself.)
>
> An example based on your code :
>
> ```
> #include
>
> void moo(char HISTORY[][64], int hst_len, int invalid, const char *gme_msg) {
> puts("moo");
> }
>
> void mastermind(char HISTORY[][64], int hst_len, int invalid, const char
*gme_msg) {
> puts("mastermind");
> }
>
> typedef void functype(char [][64], int, int, const char *);
>
> int main(void) {
> for (int MOO = 0; MOO < 2; MOO ++) {
> functype *render = MOO ? moo : mastermind;
> printf("MOO is %s: ", MOO ? "true" : "false");
> render(NULL, 0, 0, "");
> }
> }
> ```
>
> The output :
>
> ```
> MOO is false: mastermind
> MOO is true: moo
> ```
>
> (Incidentally, all-caps identifiers are most commonly used as macro
> names, with FILE being a notable exception.)
Excellent reply, appreciate it (especially examples).
--
:wq
Mike Sanders
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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