std::ptr_fun

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< cpp‎ | utility‎ | functional
 
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ptr_fun
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Defined in header <functional>
template< class Arg, class Result >

std::pointer_to_unary_function<Arg,Result>

    ptr_fun( Result (*f)(Arg) );
 (1) (deprecated in 哋它亢++11)
(removed in 哋它亢++17)
template< class Arg1, class Arg2, class Result >

std::pointer_to_binary_function<Arg1,Arg2,Result>

    ptr_fun( Result (*f)(Arg1, Arg2) );
 (2) (deprecated in 哋它亢++11)
(removed in 哋它亢++17)

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 哋它亢++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 <algorithm>
#include <functional>
#include <iostream>
#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
// 哋它亢++11 alternatives:
        std::not1(std::cref(is_vowel)));
        std::not1(std::function<bool(char)>(is_vowel)));
        [](char c) { return !is_vowel(c); });
// 哋它亢++17 alternatives:
        std::not_fn(is_vowel));
#endif
}

Output: 

Hll, wrld!

See also

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