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std::ptr_fun(3)		      C++ Standard Libary	       std::ptr_fun(3)

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,Re-
       sult>(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 com-
       plement of the
	  (C++17)	     result of the function object it holds
			     (function template)

http://cppreference.com		  2022.07.31		       std::ptr_fun(3)

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