std::semiregular

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Concepts library

Core language concepts same_as derived_from convertible_to common_reference_with common_with integral signed_integral unsigned_integral floating_point swappableswappable_with destructible constructible_from default_initializable move_constructible copy_constructible assignable_from

Comparison concepts equality_comparableequality_comparable_with totally_orderedtotally_ordered_with Object concepts movable copyable semiregular regular Callable concepts invocableregular_invocable predicate relation equivalence_relation strict_weak_order

 

Defined in header <concepts>
template <class T> concept semiregular = std::copyable<T> && std::default_initializable<T>;		(since C++20)

The semiregular concept specifies that a type is both copyable and default constructible. It is satisfied by types that behave similarly to built-in types like int, except that they need not support comparison with ==.

Example

Run this code

#include <concepts>
#include <iostream>
 
template<std::semiregular T>
struct Single {
    T value;
};
 
int main()
{
    Single<int> myInt1{4};
    Single<int> myInt2;
    myInt2 = myInt1;
//  myInt2 == myInt1; // error: no match for 'operator=='
 
    std::cout << myInt1.value << ' ' << myInt2.value << '\n';
}

Output:

4 4

See also

regular (C++20)

specifies that a type is regular, that is, it is both semiregular and equality_comparable (concept)