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#include #include #include #include #include #include #include // C++ return multiple value// 1.returned value,reference parameterbool func(const std::string& in,std::string& out1,std::string& out2){ if(in.size() == 0) return false; out1 = "hello"; out2 = "world"; return true;}// 2.tuplestd::tuple func(const std::string& in){ if(in.size() == 0) return std::make_tuple(false,"",""); return std::make_tuple(true,"hello0","world0");}// 3.pairnamespace pair{ struct Out{ std::string out1{ }; std::string out2{ }; };}std::pair func1(const std::string& in){ pair::Out o; if(in.size() == 0){ return { false,o};} o.out1 = "hello1"; o.out2 = "world1"; return { true,o};}// 4.optionalstd::optional func2(const std::string& in){ pair::Out o; if(in.size() == 0) return std::nullopt; o.out1 = "hello2"; o.out2 = "world2"; return { o};}// 5.variantstd::variant func3(const std::string& in){ std::variant re; if(in.size() == 0){ re = bool{ }; }else{ pair::Out o; o.out1 = "hello3"; o.out2 = "world3"; re = o; } return { re};}// 6. anystd::any func4(const std::string& in){ if(in.size() == 0) return bool{ }; pair::Out o; o.out1 = "hello4"; o.out2 = "world4"; return { o};}int main(){ std::string s1,s2; int status = func("hi",s1,s2); if(status){ std::cout < << std::endl; std::cout < << std::endl; } //tuple返回，结构化绑定 c++17 if(auto [status,out1,out2] = func("hi");status){ std::cout < << std::endl; std::cout < << std::endl; } //pair返回，结构化绑定 if(auto [status,o] = func1("hi");status){ std::cout << o.out1 << std::endl; std::cout << o.out2 << std::endl; } //optional 返回 if(auto ret = func2("hi");ret.has_value()){ std::cout < out1<< std::endl; std::cout < out2<< std::endl; } //variant if(auto ret = func3("hi");!std::get_if (&ret)){ std::cout < (ret).out1 << std::endl; std::cout < (ret).out2 << std::endl; } //any if(auto ret = func4("hi");ret.type() != typeid(bool)){ auto o = std::any_cast (ret); std::cout << o.out1 << std::endl; std::cout << o.out2 << std::endl; }}
此篇主要涉及到 C++17，如有疑问请留言或者参考。
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