C++ named requirements: UnaryTypeTrait (since C++11)
A UnaryTypeTrait is a class template that describes a property of its template type parameter with an integral_constant (typically bool_constant) specialization.
Requirements
- DefaultConstructible and CopyConstructible
- Takes one template type parameter (additional template parameters are optional and allowed)
- Publicly and unambiguously derived from a specialization of
integral_constant, known as its base characteristic - The member names of the base characteristic are not hidden and are unambiguously available
Standard library
The following type properties all satisfy UnaryTypeTrait.
- Primary type categories
- Composite type categories
- Type properties
- Supported operations
- Property queries
The following standard library class templates also satisfy UnaryTypeTrait.
| pub | integral_constant(C++11) | compile-time constant of specified type with specified value |
| pub | negation(C++17) | logical NOT metafunction |
| pub | std::tuple_size<std::tuple>(C++11) | obtains the size of tuple at compile time |
| pub | std::tuple_size<std::array>(C++11) | obtains the size of an array |
| pub | std::tuple_size<std::pair>(C++11) | obtains the size of a pair |
| pub | variant_size variant_size_v(C++17) | obtains the size of the variant's list of alternatives at compile time |
| pub | is_bind_expression(C++11) | indicates that an object is std::bind expression or can be used as one |
| pub | is_placeholder(C++11) | indicates that an object is a standard placeholder or can be used as one |
| pub | is_execution_policy(C++17) | test whether a class represents an execution policy |