ptr_fun(3C++)

Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

NAME

ptr_fun

- A function that is overloaded to adapt a pointer to a function, to take the place of a function.

SYNOPSIS

#include <functional>
template<class Arg, class Result>
pointer_to_unary_function<Arg, Result>

ptr_fun (Result (∗f)(Arg));

template<class Arg1, class Arg2, class Result>
pointer_to_binary_function<Arg1, Arg2, Result>

ptr_fun (Result (∗x)(Arg1, Arg2));

DESCRIPTION

The pointer_to_unary_function and pointer_to_binary_function classes encapsulate pointers to functions and use operator() so that the resulting object serves as a function object for the function.

The ptr_fun function is overloaded to create instances of pointer_to_unary_function or pointer_to_binary_function when included with the appropriate pointer to a function.

EXAMPLE

//
// pnt2fnct.cpp
//

#include <functional>
#include <deque>
#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;

//Create a function

int factorial(int x)

{

int result = 1;
for(int i = 2; i <= x; i++)

result ∗= i;

return result;

}

int main()

{

//Initialize a deque with an array of ints

int init[7] = {1,2,3,4,5,6,7};
deque<int> d(init, init+7);

//Create an empty vector to store the factorials

vector<int> v((size_t)7);

//Transform the numbers in the deque to their
//factorials and store in the vector

transform(d.begin(), d.end(), v.begin(),

ptr_fun(factorial));

//Print the results

cout << "The following numbers: " << endl << " ";
copy(d.begin(),d.end(),

ostream_iterator<int,char>(cout," "));

cout << endl << endl;
cout << "Have the factorials: " << endl << " ";
copy(v.begin(),v.end(),

ostream_iterator<int,char>(cout," "));

return 0;

}

Program Output

The following numbers:

1 2 3 4 5 6 7

Have the factorials:

1 2 6 24 120 720 5040

WARNINGS

If your compiler does not support default template parameters, you always need to supply the Allocator template argument. For instance, you need to write:

vector<int, allocator<int> >

instead of:

vector<int>

If your compiler does not support namespaces, then you do not need the using declaration for std.