ptr_fun(3C++) - ptr_fun(3C++)
Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.
NAMEptr_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 OutputThe 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.
SEE ALSO
Function_Objects, pointer_to_binary_function, pointer_to_unary_function
Rogue Wave Software 02 Apr 1998 ptr_fun(3C++)
