Correct Way to Define a Predicate Function in C++

Question

I\'m trying to write predicate function for use with STL algorithms. I see that they are two ways to define a predicate:

(1) Use a simple function as below:

Answer 1

I guess it's because the type of c.isEven() is,

bool (checker::*)(unsigned int) // member function of class

which may not be expected by find_if(). std::find_if should be expecting either a function pointer (bool (*)(unsigned int)) or a function object.

Edit: Another constraint: A non-static member function pointer must be called by the class object. In your case, even if you succeed to pass the member function then still find_if() will not have any information about any checker object; so it doesn't make sense to have find_if() overloaded for accepting a member function pointer argument.

Note: In general c.isEven is not the right way to pass member function pointer; it should be passed as, &checker::isEven.