[meta.unary.cat]

The primary type categories correspond to the descriptions given in subclause [basic.types] of the C++ standard.

For any given type T, the result of applying one of these templates to T and to cv T shall yield the same result.

:

For any given type T, exactly one of the primary type categories has a value member that evaluates to true.

— end note

]

Table 47: Primary type category predicates [tab:meta.unary.cat]

Template	Condition	Comments
template<class T> struct is_void;	T is void
template<class T> struct is_null_pointer;	T is nullptr_t ([basic.fundamental])
template<class T> struct is_integral;	T is an integral type ([basic.fundamental])
template<class T> struct is_floating_point;	T is a floating-point type ([basic.fundamental])
template<class T> struct is_array;	T is an array type ([basic.compound]) of known or unknown extent	Class template array is not an array type.
template<class T> struct is_pointer;	T is a pointer type ([basic.compound])	Includes pointers to functions but not pointers to non-static members.
template<class T> struct is_lvalue_reference;	T is an lvalue reference type ([dcl.ref])
template<class T> struct is_rvalue_reference;	T is an rvalue reference type ([dcl.ref])
template<class T> struct is_member_object_pointer;	T is a pointer to data member
template<class T> struct is_member_function_pointer;	T is a pointer to member function
template<class T> struct is_enum;	T is an enumeration type ([basic.compound])
template<class T> struct is_union;	T is a union type ([basic.compound])
template<class T> struct is_class;	T is a non-union class type ([basic.compound])
template<class T> struct is_function;	T is a function type ([basic.compound])

20 General utilities library [utilities]