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Defined in header <utility> | ||
template<class T> constexprstd::add_const_t<T>& as_const( T& t)noexcept; | (1) | (since C++17) |
template<class T> void as_const(const T&&)= delete; | (2) | (since C++17) |
Contents |
template<class T>constexprstd::add_const_t<T>& as_const(T& t)noexcept{return t;} |
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_as_const | 201510L | (C++17) | std::as_const |
#include <cassert>#include <string>#include <type_traits>#include <utility> int main(){std::string mutableString="Hello World!";auto&& constRef= std::as_const(mutableString); mutableString.clear();// OK// constRef.clear(); // Error: 'constRef' is 'const' qualified,// but 'clear' is not marked const assert(&constRef==&mutableString);assert(&std::as_const(mutableString)==&mutableString); using ExprType=std::remove_reference_t<decltype(std::as_const(mutableString))>; static_assert(std::is_same_v<std::remove_const_t<ExprType>,std::string>,"ExprType should be some kind of string."); static_assert(!std::is_same_v<ExprType,std::string>,"ExprType shouldn't be a mutable string.");}
(C++11) | checks if a type is const-qualified (class template)[edit] |
(C++11)(C++11)(C++11) | addsconst and/orvolatile specifiers to the given type (class template)[edit] |
(C++11)(C++11)(C++11) | removesconst and/orvolatile specifiers from the given type (class template)[edit] |
converts aview into aconstant_range(class template)(range adaptor object)[edit] |
