Variable templates for type traits (library fundamentals TS)

From cppreference.com
C++
Experimental
Library fundamentals

Version 1 of the C++ Extensions for Library Fundamentals provides a number of constexpr variable templates for type traits classes, as well as other similar class templates with public ::value members.

Unless otherwise noted, the following variable templates are defined in the std::experimental namespace.

Type traits

Primary type categories
Variable template Value
template < class T > constexpr bool is_void_v = std:: is_void < T > :: value ;
template < class T > constexpr bool is_null_pointer_v = std:: is_null_pointer < T > :: value ;
template < class T > constexpr bool is_integral_v = std:: is_integral < T > :: value ;
template < class T > constexpr bool is_floating_point_v = std:: is_floating_point < T > :: value ;
template < class T > constexpr bool is_array_v = std:: is_array < T > :: value ;
template < class T > constexpr bool is_pointer_v = std:: is_pointer < T > :: value ;
template < class T > constexpr bool is_lvalue_reference_v = std:: is_lvalue_reference < T > :: value ;
template < class T > constexpr bool is_rvalue_reference_v = std:: is_rvalue_reference < T > :: value ;
template < class T > constexpr bool is_member_object_pointer_v = std:: is_member_object_pointer < T > :: value ;
template < class T > constexpr bool is_member_function_pointer_v = std:: is_member_function_pointer < T > :: value ;
template < class T > constexpr bool is_enum_v = std:: is_enum < T > :: value ;
template < class T > constexpr bool is_union_v = std:: is_union < T > :: value ;
template < class T > constexpr bool is_class_v = std:: is_class < T > :: value ;
template < class T > constexpr bool is_function_v = std:: is_function < T > :: value ;
Composite type categories
Variable template Value
template < class T > constexpr bool is_reference_v = std:: is_reference < T > :: value ;
template < class T > constexpr bool is_arithmetic_v = std:: is_arithmetic < T > :: value ;
template < class T > constexpr bool is_fundamental_v = std:: is_fundamental < T > :: value ;
template < class T > constexpr bool is_object_v = std:: is_object < T > :: value ;
template < class T > constexpr bool is_scalar_v = std:: is_scalar < T > :: value ;
template < class T > constexpr bool is_compound_v = std:: is_compound < T > :: value ;
template < class T > constexpr bool is_member_pointer_v = std:: is_member_pointer < T > :: value ;
Type properties
Variable template Value
template < class T > constexpr bool is_const_v = std:: is_const < T > :: value ;
template < class T > constexpr bool is_volatile_v = std:: is_volatile < T > :: value ;
template < class T > constexpr bool is_trivial_v = std:: is_trivial < T > :: value ;
template < class T > constexpr bool is_trivially_copyable_v = std:: is_trivially_copyable < T > :: value ;
template < class T > constexpr bool is_standard_layout_v = std:: is_standard_layout < T > :: value ;
template < class T > constexpr bool is_pod_v = std:: is_pod < T > :: value ;
template < class T > constexpr bool is_literal_type_v = std:: is_literal_type < T > :: value ;
template < class T > constexpr bool is_empty_v = std:: is_empty < T > :: value ;
template < class T > constexpr bool is_polymorphic_v = std:: is_polymorphic < T > :: value ;
template < class T > constexpr bool is_abstract_v = std:: is_abstract < T > :: value ;
template < class T > constexpr bool is_final_v = std:: is_final < T > :: value ;
template < class T > constexpr bool is_signed_v = std:: is_signed < T > :: value ;
template < class T > constexpr bool is_unsigned_v = std:: is_unsigned < T > :: value ;
Supported operations
Variable template Value
template < class T, class ... Args > constexpr bool is_constructible_v = std:: is_constructible < T, Args... > :: value ;
template < class T, class ... Args > constexpr bool is_trivially_constructible_v = std:: is_trivially_constructible < T, Args... > :: value ;
template < class T, class ... Args > constexpr bool is_nothrow_constructible_v = std:: is_nothrow_constructible < T, Args... > :: value ;
template < class T > constexpr bool is_default_constructible_v = std:: is_default_constructible < T > :: value ;
template < class T > constexpr bool is_trivially_default_constructible_v = std:: is_trivially_default_constructible < T > :: value ;
template < class T > constexpr bool is_nothrow_default_constructible_v = std:: is_nothrow_default_constructible < T > :: value ;
template < class T > constexpr bool is_copy_constructible_v = std:: is_copy_constructible < T > :: value ;
template < class T > constexpr bool is_trivially_copy_constructible_v = std:: is_trivially_copy_constructible < T > :: value ;
template < class T > constexpr bool is_nothrow_copy_constructible_v = std:: is_nothrow_copy_constructible < T > :: value ;
template < class T > constexpr bool is_move_constructible_v = std:: is_move_constructible < T > :: value ;
template < class T > constexpr bool is_trivially_move_constructible_v = std:: is_trivially_move_constructible < T > :: value ;
template < class T > constexpr bool is_nothrow_move_constructible_v = std:: is_nothrow_move_constructible < T > :: value ;
template < class T, class U > constexpr bool is_assignable_v = std:: is_assignable < T, U > :: value ;
template < class T, class U > constexpr bool is_trivially_assignable_v = std:: is_trivially_assignable < T, U > :: value ;
template < class T, class U > constexpr bool is_nothrow_assignable_v = std:: is_nothrow_assignable < T, U > :: value ;
template < class T > constexpr bool is_copy_assignable_v = std:: is_copy_assignable < T > :: value ;
template < class T > constexpr bool is_trivially_copy_assignable_v = std:: is_trivially_copy_assignable < T > :: value ;
template < class T > constexpr bool is_nothrow_copy_assignable_v = std:: is_nothrow_copy_assignable < T > :: value ;
template < class T > constexpr bool is_move_assignable_v = std:: is_move_assignable < T > :: value ;
template < class T > constexpr bool is_trivially_move_assignable_v = std:: is_trivially_move_assignable < T > :: value ;
template < class T > constexpr bool is_nothrow_move_assignable_v = std:: is_nothrow_move_assignable < T > :: value ;
template < class T > constexpr bool is_destructible_v = std:: is_destructible < T > :: value ;
template < class T > constexpr bool is_trivially_destructible_v = std:: is_trivially_destructible < T > :: value ;
template < class T > constexpr bool is_nothrow_destructible_v = std:: is_nothrow_destructible < T > :: value ;
template < class T > constexpr bool has_virtual_destructor_v = std:: has_virtual_destructor < T > :: value ;
Property queries
Variable template Value
template < class T > constexpr std:: size_t alignment_of_v = std:: alignment_of < T > :: value ;
template < class T > constexpr std:: size_t rank_v = std:: rank < T > :: value ;
template < class T, unsigned I = 0 > constexpr std:: size_t extent_v = std:: extent < T, I > :: value ;
Type relationships
Variable template Value
template < class T, class U > constexpr bool is_same_v = std:: is_same < T, U > :: value ;
template < class Base, class Derived > constexpr bool is_base_of_v = std:: is_base_of < Base, Derived > :: value ;
template < class From, class To > constexpr bool is_convertible_v = std:: is_convertible < From, To > :: value ;

Other variable templates

std::ratio comparison
Variable template Value
Defined in header <experimental/ratio>
template < class R1, class R2 > constexpr bool ratio_equal_v = std:: ratio_equal < R1, R2 > :: value ;
template < class R1, class R2 > constexpr bool ratio_not_equal_v = std:: ratio_not_equal < R1, R2 > :: value ;
template < class R1, class R2 > constexpr bool ratio_less_v = std:: ratio_less < R1, R2 > :: value ;
template < class R1, class R2 > constexpr bool ratio_less_equal_v = std:: ratio_less_equal < R1, R2 > :: value ;
template < class R1, class R2 > constexpr bool ratio_greater_v = std:: ratio_greater < R1, R2 > :: value ;
template < class R1, class R2 > constexpr bool ratio_greater_equal_v = std:: ratio_greater_equal < R1, R2 > :: value ;
Miscellaneous
Variable template Value
Defined in header <experimental/tuple>
template < class T > constexpr std:: size_t tuple_size_v = std:: tuple_size < T > :: value ;
Defined in header <experimental/chrono>
template < class Rep > constexpr bool treat_as_floating_point_v = std:: chrono :: treat_as_floating_point < Rep > :: value ; [1]
template < class T > constexpr bool is_error_code_enum_v = std:: is_error_code_enum < T > :: value ;
template < class T > constexpr bool is_error_condition_enum_v = std:: is_error_condition_enum < T > :: value ;
Defined in header <experimental/functional>
template < class T > constexpr bool is_bind_expression_v = std:: is_bind_expression < T > :: value ;
template < class T > constexpr int is_placeholder_v = std:: is_placeholder < T > :: value ;
Defined in header <experimental/memory>
template < class T, class Alloc > constexpr bool uses_allocator_v = std:: uses_allocator < T, Alloc > :: value ;

Notes

[1]: Defined in the std::chrono::experimental namespace.

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