Understanding typedefs for function pointers in C?

Question

I have always been a bit stumped when I read other peoples' code which had typedefs for pointers to functions with arguments. I recall that it took me a while to get around to such a definition while trying to understand a numerical algorithm written in C a while ago. So, could you share your tips and thoughts on how to write good typedefs for pointers to functions (Do's and Do not's), as to why are they useful and how to understand others' work? Thanks!

Answer 1

Take the following example:

typedef int( *func_ptr )( int param_one, double param_two );

This statement creates a variable type called func_ptr which will (must) points

to a function that takes two parameters, an integer and a double and returns and integer.

If you define a function such as:

int sample( int one, double two ) {

int result = one;

if ( two > 2.0 ) result *= 2;

return result;

}; // end sample

and assign it to a variable of type func_ptr:

func_ptr var_name = sample;