template<class T>
struct remove_const;

The member typedef type denotes the type formed by removing any top-level const-qualifier from T.

template<class T>
struct remove_volatile;

The member typedef type denotes the type formed by removing any top-level volatile-qualifier from T.

template<class T>
struct remove_cv;

The member typedef type denotes the type formed by removing any top-level cv-qualifiers from T.

template<class T>
struct add_const;

The member typedef type denotes const T.

template<class T>
struct add_volatile;

The member typedef type denotes volatile T.

template<class T>
struct add_cv;

The member typedef type denotes add_const_t<add_volatile_t<T>>.