C++

Reference

<functional>

function template
<functional>

std::ptr_fun

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 (*f)(Arg1,Arg2));
Convert function pointer to function object
Returns a function object that encapsulates function f.

Function objects are objects whose class defines member function operator(). This member function allows the object to be used with the same syntax as a regular function call. Several standard algorithms and adaptors are designed to be used with function objects.

It is defined with the same behavior as:

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template <class Arg, class Result>
  pointer_to_unary_function<Arg,Result> ptr_fun (Result (*f)(Arg))
{
  return pointer_to_unary_function<Arg,Result>(f);
}

template <class Arg1, class Arg2, class Result>
  pointer_to_binary_function<Arg1,Arg2,Result> ptr_fun (Result (*f)(Arg1,Arg2))
{
  return pointer_to_binary_function<Arg1,Arg2,Result>(f);
}

Template parameters

Arg, Arg1, Arg2
Types of the function's arguments.
Result
Function's return type.

Parameters

f
Pointer to a function, taking either one argument (of type Arg) or two arguments (of types Arg1 and Arg2) and returning a value of type Result.

Return value

A function object equivalent to f.
pointer_to_unary_function and pointer_to_binary_function are function object types, derived respectively from unary_function and binary_function.

Example

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// ptr_fun example
#include <iostream>
#include <functional>
#include <algorithm>
#include <cstdlib>
#include <numeric>
using namespace std;

int main () {
  char* foo[] = {"10","20","30","40","50"};
  int bar[5];
  int sum;
  transform (foo, foo+5, bar, ptr_fun(atoi) );
  sum = accumulate (bar, bar+5, 0);
  cout << "sum = " << sum << endl;
  return 0;
}

Possible output:

sum = 150


See also

mem_fun
Convert member function to function object (pointer version) (function template)
pointer_to_unary_function
Generate unary function object class from pointer (class template)
pointer_to_binary_function
Generate binary function object class from pointer (class template)
unary_function
Unary function object base class (class template)