Standard Template Library Programmer's Guide

polymorphism involves calling member functions through pointers or references.

As with many other adaptors, it is usually inconvenient to use mem_fun1_t's constructor directly. It is usually better to use the helper function mem_fun [2] instead.

Example

struct Operation {
 virtual double eval(double) = 0;
};
struct Square : public Operation {
 double eval(double x) { return x * x; }
};
struct Negate : public Operation {
 double eval(double x) { return –x; }
};
int main() {
 vector<Operation*> operations;
 vector<double> operands;
 operations.push_back(new Square);
 operations.push_back(new Square);
 operations.push_back(new Negate);
 operations.push_back(new Negate);
 operations.push_back(new Square);
 operands.push_back(1);
 operands.push_back(2);
 operands.push_back(3);
 operands.push_back(4);
 operands.push_back(5);
 transform(operations.begin(), operations.end(), operands.begin(), ostream_iterator<double>(cout, '
'), mem_fun(Operation::eval));
}

Definition

Defined in the standard header functional, and in the nonstandard backward-compatibility header function.h.

Template parameters

Parameter	Description
Result	The member function's return type.
X	The class whose member function the mem_fun1_t invokes.
Arg	The member function's argument type.

Model of

Adaptable Binary Function

Type requirements

• X has at least one member function that takes a single argument of type Arg and that returns a value of type Result. [1]

Public base classes

binary_function<X*, Arg, Result>

Members

Member	Where defined	Description
first_argument_type	Adaptable Binary Function	The type of the first argument: X*
second_argument_type	Adaptable Binary Function	The type of the second argument: Arg
result_type	Adaptable Binary Function	The type of the result: Result
Result operator()(X* x, Arg a) const	Binary Function	Function call operator. Invokes x->f(a), where f is the member function that was passed to the constructor.
explicit mem_fun1_t(Result (X::*f)(Arg))	mem_fun1_t	See below.
template <class Result, class X, class Arg> mem_fun1_t<Result, X, Arg> mem_fun (Result (X::*f)(Arg)); [2]	mem_fun1_t