Thread: Function pointer

Originally Posted by George2

1. I think pmf is a type of function pointer, the return type of the function is R and the function is a member function of type (class) T. Is my understanding correct?

That first statement is weird. There must be some missing code.
Could it be some kind of declaration of function pointer? Still, it's missing ; at the end.

2. If yes, what is the parameter list of the function? Empty parameter list?

Yes.

3. I doubt whether it is useful to define a function pointer with empty parameter list -- too restricted.

Not always. You can use events for example, where you call back saying an event has finished or some such. Also useful when using dynamic linking of dlls. You get a function address dynamically from a dll, and call it using a function pointer.
Sometimes these functions don't take any arguments.

Originally Posted by George2

Hello everyone,


In the following statements,

Code:

template <class R, class T> class mem_fun_t : public unary_function <T*, R>

{

R (T::*pmf)()
...
}

1. I think pmf is a type of function pointer, the return type of the function is R and the function is a member function of type (class) T. Is my understanding correct?

Yes.

2. If yes, what is the parameter list of the function? Empty parameter list?

Correct.

3. I doubt whether it is useful to define a function pointer with empty parameter list -- too restricted.

Yes, it's restricted in the sense that you can't pass in any parameters.

But some functions are fine without parameters. It's a typical case of "right tool for the job" - no point in adding parameters to a function if you don't actually need any. For example, this function may be to fetch an object R out of the T class, which only holds ONE R object - in which case, it's perfectly fine to do that without any parameters. Without a wider scope to understand the meaning of the code, it's impossible to say if it's "too restricted" or "just right".

--
Mats