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:
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)