C expert programming-Analysis of the signal function prototype declaration {void (* signal (INT Sig, void (* func) (INT)} (2)

In the ANSI standard, the signal () statement is as follows:

Void (* signal (INT Sig, void (* func) (INT)

Signal is a function that returns a function pointer. the function that the latter points to (the return value of signal) accepts an int parameter and returns void. The signal function has two parameters: SIG (INT type) and func (void (*) (INT ).

Void (* func) (INT) is a function pointer. The function to which it points accepts an int parameter, and the return value is void.

The following is simplified using typedef:

Typedef void (* ptr_to_func) (INT );

Ptr_to_func signal (INT, ptr_to_func );

An example on the Internet:

# Include <stdio. h>

Enum{Red, green, blue };

Void outputsignal (intSIG)
{
Printf ("the signal you/'ve input is :");

Switch(SIG)
{
CaseRed:
Puts ("red! ");
Break;

CaseGreen:
Puts ("green! ");
Break;

CaseBlue:
Puts ("blue! ");
Break;
}
}

Void (* signal (INT Sig, void (* func) (INT) (int)
{
Puts ("Hello, world! ");

Func (SIG );

ReturnFunc;
}

Int main (void)
{
(* Signal (Green ,&Outputsignal) (red );

Return 0;
}

Output:

Hello, world!

The signal you 've input is: Green!

The signal you 've input is: red!