C++: Passing a function to a function

[TheLonelyPhoenix]

I'm trying to build a class which allows a member function to take another function as a parameter. However, I can't seem to find a good example of how this is done. I particular I need to know how to structure the function definition for this.

I hope that made sense. Any ideas?

 

[Nothinman]

You can't pass a function around, but you can pass around a function address.

 

[TheLonelyPhoenix]

Originally posted by: Nothinman
You can't pass a function around, but you can pass around a function address.

I know it involves using a void * to pass the function. Is that what you mean?

 

[DaveSimmons]

Look up the qsort() ANSI C function and see how they pass the comparison function. msdn.microsoft.com has a nice sample.

 

[TheLonelyPhoenix]

Looked it up, and was thouroughly confused by it. 🙁

 

[kylef]

In C, you use function pointers to refer to anonymous functions. Then you'd declare your own function that accepts a "pointer to function" as one of its parameters. The caller would pass a pointer to the desired function, and whoila... you have just passed a function as a parameter.



In C++ you can use an object that wraps a function pointer, called a "functor". You can read more about those at this Function Pointer site.

 

[kylef]

BTW, if you're trying to pass a C++ member function, then the syntax is slightly more complicated. You need what is called a "pointer to a member."

int (ClassName::*pMember)( /* parameter types here */ );

See Stroustrup 3rd ed. section 15.5, "Pointers to members."