Specifies that a type is aliteral type. Literal types are the types ofconstexpr variables and they can be constructed, manipulated, and returned fromconstexpr functions.

Note: the standard doesn't define a named requirement with this name. This is a type category defined by the core language. It is included here as a named requirement only for consistency.

[edit]Requirements

A literal type is any of the following:

• scalar type;
• reference type;
• anarray of literal type;
• possibly cv-qualified class type that has all of the following properties:

• has atrivial(until C++20)constexpr(since C++20)destructor,
• all of its non-static non-variant data members and base classes are of non-volatile literal types, and
• is one of

• anaggregate union type that

• has novariant members, or
• has at least one variant member of non-volatile literal type,

• a non-unionaggregate type, and each of itsanonymous union members

• has novariant members, or
• has at least one variant member of non-volatile literal type,

• a type with at least oneconstexpr (possibly template) constructor that is not a copy or move constructor.

[edit]Notes

A type can be literal even if all of its constexpr constructors are deleted, inaccessible, or cannot participate in overload resolution.

struct A{constexpr A(int)= delete;char c;};// A is a literal typeconstexpr A v=std::bit_cast<A>('0');// OK in C++20// v has literal type and thus can be constexpr

[edit]Example

#include <cstddef>#include <iostream>#include <stdexcept> class conststr// conststr is a literal type{constchar* p;std::size_t sz;public:template<std::size_t N>constexpr conststr(constchar(&a)[N]): p(a), sz(N-1){} constexprchar operator[](std::size_t n)const{return n< sz? p[n]:throwstd::out_of_range("");} constexprstd::size_t size()const{return sz;}}; constexprstd::size_t count_lower(conststr s){std::size_t c{};for(std::size_t n{}; n!= s.size();++n)if('a'<= s[n]&& s[n]<='z')++c;return c;} // An output function that requires a compile-time constant N, for testingtemplate<int N>struct constN{    constN(){std::cout<< N<<'\n';}}; int main(){std::cout<<"The number of lowercase letters in\"Hello, world!\" is ";    constN<count_lower("Hello, world!")>();// the string literal is implicitly// converted to conststr}

The number of lowercase letters in "Hello, world!" is 9

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit]See also

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