#pragma once #include <util/generic/string.h> #include <util/generic/variant.h> namespace NYT { //////////////////////////////////////////////////////////////////////////////// //! A concise way of creating a functor with an overloaded operator(). /*! * Very useful for std::visit-ing variants. For example: * * std::visit(TOverloaded{ * [] (int i) { printf("The variant holds an int: %d!", i); }, * [] (const std::string& s) { printf("The variant holds a string: '%s'!", s); } * }, variantVariable); */ template<class... Ts> struct TOverloaded : Ts... { using Ts::operator()...; }; template<class... Ts> TOverloaded(Ts...) -> TOverloaded<Ts...>; //////////////////////////////////////////////////////////////////////////////// //! An alternative to std::visit that takes its variant argument first. /*! * This deprives it of being able to visit a Cartesian product of variants but * in exchange allows to receive multiple visitor functors. All of operator()s * these functors have are used to visit the variant after a single unified * overload resolution. For example: * * Visit(variantVariable, * [] (int i) { printf("The variant holds an int: %d!", i); }, * [] (const std::string& s) { printf("The variant holds a string: '%s'!", s); }); */ template <class T, class... U> auto Visit(T&& variant, U&&... visitorOverloads) { return std::visit(TOverloaded{std::forward<U>(visitorOverloads)...}, std::forward<T>(variant)); } //////////////////////////////////////////////////////////////////////////////// } // namespace NYT