NAME

std::ptr_fun - std::ptr_fun

Synopsis

Defined in header <functional>
template< class Arg, class Result >
(deprecated in C++11)
std::pointer_to_unary_function<Arg,Result> (1) (removed in C++17)

ptr_fun( Result (*f)(Arg) );
template< class Arg1, class Arg2, class Result >
(deprecated in C++11)
std::pointer_to_binary_function<Arg1,Arg2,Result> (2) (removed in C++17)

ptr_fun( Result (*f)(Arg1, Arg2) );

Creates a function wrapper object (either std::pointer_to_unary_function or
std::pointer_to_binary_function), deducing the target type from the template
arguments.

1) Effectively calls std::pointer_to_unary_function<Arg,Result>(f).
2) Effectively calls std::pointer_to_binary_function<Arg1,Arg2,Result>(f).

This function and the related types are deprecated as of C++11 in favor of the more
general std::function and std::ref, both of which create callable adaptor-compatible
function objects from plain functions.

Parameters

f - pointer to a function to create a wrapper for

Return value

A function object wrapping f.

Exceptions

May throw implementation-defined exceptions.

Example

// Run this code

#include <iostream>
#include <algorithm>
#include <functional>
#include <string_view>

constexpr bool is_vowel(char c)
{
return std::string_view{"aeoiuAEIOU"}.find(c) != std::string_view::npos;
}

int main()
{
std::string_view s = "Hello, world!";
std::ranges::copy_if(s, std::ostreambuf_iterator<char>(std::cout),
std::not1(std::ptr_fun(is_vowel)));
#if 0
// C++11 alternatives:
std::not1(std::cref(is_vowel)));
std::not1(std::function<bool(char)>(is_vowel)));
[](char c){ return !is_vowel(c); });
// C++17 alternatives:
std::not_fn(is_vowel));
#endif
}

Output:

Hll, wrld!

See also

function wraps callable object of any copy constructible type with
(C++11) specified function call signature
(class template)
move_only_function wraps callable object of any type with specified function call
(C++23) signature
(class template)
invoke invokes any Callable object with given arguments
invoke_r and possibility to specify return type
(C++17) (since C++23)
(C++23) (function template)
not_fn Creates a function object that returns the complement of the
(C++17) result of the function object it holds
(function template)