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std::variant::visit(3)	      C++ Standard Libary	std::variant::visit(3)

NAME
       std::variant::visit - std::variant::visit

Synopsis
	  template<	   class       Self,	   class       Visitor	     >
       (1) (since C++26)
	  constexpr decltype(auto) visit( this Self&& self, Visitor&& vis );
	  template<    class	R,    class    Self,	class	 Visitor     >
       (2) (since C++26)
	  constexpr R visit( this Self&& self, Visitor&& vis );

	  Applies the visitor vis (a Callable that can be called with any com-
       bination	of types
	  from the variant) to the variant held	by self.

	  Given	 type V	as decltype(std::forward_like<Self>(std::declval<vari-
       ant>())), the
	  equivalent call is:

	  1) return std::visit(std::forward<Visitor>(vis), (V) self);.
	  2) return std::visit<R>(std::forward<Visitor>(vis), (V) self);.

Parameters
	  vis  - a Callable that accepts every possible	alternative  from  the
       variant
	  self - variant to pass to the	visitor

Return value
	  1) The result	of the std::visit invocation.
	  2)  Nothing  if R is (possibly cv-qualified) void; otherwise the re-
       sult of the
	  std::visit<R>	invocation.

Exceptions
	  Only throws if the call to std::visit	throws.

Notes
	  Feature-test macro  Value    Std     Feature
	  __cpp_lib_variant  202306L (C++26) member visit

Example
       // Run this code

	#include <iostream>
	#include <string>
	#include <variant>

	// helper type for the visitor
	template<class... Ts>
	struct overloads : Ts... { using Ts::operator()...; };

	int main()
	{
	    std::variant<int, std::string> var1{42}, var2{"abc"};

	    auto use_int = [](int i){ std::cout	<< "int	= " << i << '\n'; };
	    auto use_str = [](std::string s){ std::cout	<< "string = " << s <<
       '\n'; };

	#if (__cpp_lib_variant >= 202306L)
	    var1.visit(overloads{use_int, use_str});
	    var2.visit(overloads{use_int, use_str});
	#else
	    std::visit(overloads{use_int, use_str}, var1);
	    std::visit(overloads{use_int, use_str}, var2);
	#endif
	}

Output:
	int = 42
	string = abc

http://cppreference.com		  2024.06.10		std::variant::visit(3)

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