.\" ident @(#)ptr_fun.3
.\" Standard Template Library
.\" $$RW_INSERT_HEADER "slyrs.man"
.TH ptr_fun 3C++ "02 Apr 1998" "Rogue Wave Software" "-"
.ce2
Standard C++ Library   
Copyright 1998, Rogue Wave Software, Inc.   

.SH NAME

\f2ptr_fun\fP

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



.SH  SYNOPSIS


.br
#include <functional>
.br
template<class Arg, class Result>
.br
pointer_to_unary_function<Arg, Result>
.RE
.RS 2
ptr_fun (Result (*f)(Arg));
.RE
.RS 0

.br
template<class Arg1, class Arg2, class Result>
.br
pointer_to_binary_function<Arg1, Arg2, Result>
.RE
.RS 2
ptr_fun (Result (*x)(Arg1, Arg2));



.SH  DESCRIPTION


The pointer_to_unary_function and pointer_to_binary_function classes encapsulate pointers to functions and use \f2operator()\fP so that the resulting object serves as a function object for the function.

The \f2ptr_fun\fP 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. 



.SH  EXAMPLE



.RE
.RS 0
//
.br
// pnt2fnct.cpp
.br
//
.RE
.RS 1
#include <functional>
.br
#include <deque>
.br
#include <vector>
.br
#include <algorithm>
.br
#include <iostream>
.RE
.RS 0
using namespace std;
.br

.RE
.RS 1
//Create a function
.RE
.RS 0
int factorial(int x)
.RE
.RS 1
{
.RE
.RS 2
int result = 1;
.br
for(int i = 2; i <= x; i++)
.RE
.RS 6
result *= i;
.RE
.RS 2
return result;
.RE
.RS 1
}
.RE
.RS 0

.br
int main()
.RE
.RS 1
{
.RE
.RS 3
//Initialize a deque with an array of ints
.RE
.RS 2
int init[7] = {1,2,3,4,5,6,7};
.br
deque<int> d(init, init+7);
.RE
.RS 0

.RE
.RS 3
//Create an empty vector to store the factorials
.RE
.RS 2
vector<int> v((size_t)7);
.RE
.RS 0

.RE
.RS 3
//Transform the numbers in the deque to their 
.br
//factorials and store in the vector
.RE
.RS 2
transform(d.begin(), d.end(), v.begin(),
.RE
.RS 13
ptr_fun(factorial));
.RE
.RS 0

.RE
.RS 3
//Print the results
.RE
.RS 2
cout << "The following numbers: " << endl << "     ";
.br
copy(d.begin(),d.end(),
.RE
.RS 7
ostream_iterator<int,char>(cout," "));
.RE
.RS 0

.RE
.RS 2
cout << endl << endl;
.br
cout << "Have the factorials: " << endl << "     ";
.br
copy(v.begin(),v.end(),
.RE
.RS 7
ostream_iterator<int,char>(cout," "));
.RE
.RS 0

.RE
.RS 2
return 0;
.RE
.RS 1
}

.br
.RE
.RS 0
Program Output



.RE
.RS 0

.br
The following numbers:
.RE
.RS 4
1 2 3 4 5 6 7
.RE
.RS 0
Have the factorials:
.RE
.RS 4
1 2 6 24 120 720 5040



.SH  WARNINGS


If your compiler does not support default template parameters, you always need to supply the \f2Allocator\fP template argument. For instance, you need to write:

\f2vector<int, allocator<int> >\fP

instead of:

\f2vector<int>\fP

If your compiler does not support namespaces, then you do not need the using declaration for \f2std\fP.



.SH  SEE ALSO


Function_Objects, pointer_to_binary_function, pointer_to_unary_function