Type qualifier traits¶

Traits related to cv (const and volatile) type qualifiers, as well as reference declaration.

Reference¶

Detection traits¶

#include <actl/meta/qualifiers/detection.hpp>

template<typename T> bool ac::is_cv_v = std::is_const_v<T> && std::is_volatile_v<T>¶: Checks if the type has both const and volatile qualifiers.

template<typename T> bool ac::has_qualifiers_v = std::is_reference_v<T> || std::is_const_v<T> || std::is_volatile_v<T>¶: Checks if the type has any of const, volatile or reference qualifiers.

See tests at tests/meta/qualifiers/detection.cpp

Qualifiers copy between types¶

Traits that replace type qualifiers with the ones from the source type.

Table below shows the effect of different source types on the following destination types: int, int const, int&.

It’s important to understand the behavior of a referenced type qualifiers. Unless ac::copy_cvref_t is used:

Referenced type qualifiers of a source type don’t affect the result.
Referenced type qualifiers of a destination type are not changed.

Expression	unqualified	cv-qualified	l-value ref	r-value ref
Source type S	`char`	`char const volatile`	`char const&`	`char volatile&&`
`copy_const_t<int, S>`	`int`	`int const`	`int`	`int`
`copy_const_t<int const, S>`	`int`	`int const`	`int`	`int`
`copy_const_t<int&, S>`	`int&`	`int&`	`int&`	`int&`
`copy_volatile_t<int, S>`	`int`	`int volatile`	`int`	`int`
`copy_volatile_t<int const, S>`	`int const`	`int const volatile`	`int const`	`int const`
`copy_volatile_t<int&, S>`	`int&`	`int&`	`int&`	`int&`
`copy_cv_t<int, S>`	`int`	`int const volatile`	`int`	`int`
`copy_cv_t<int const, S>`	`int`	`int const volatile`	`int`	`int`
`copy_cv_t<int&, S>`	`int&`	`int&`	`int&`	`int&`
`copy_reference_t<int, S>`	`int`	`int`	`int&`	`int&&`
`copy_reference_t<int const, S>`	`int const`	`int const`	`int const&`	`int const&&`
`copy_reference_t<int&, S>`	`int`	`int`	`int&`	`int&&`
`copy_cvref_t<int, S>`	`int`	`int const volatile`	`int const&`	`int volatile&&`
`copy_cvref_t<int const, S>`	`int`	`int const volatile`	`int const&`	`int volatile&&`
`copy_cvref_t<int&, S>`	`int`	`int const volatile`	`int const&`	`int volatile&&`

Note

Boost.TypeTraits, for example, boost::copy_reference, don’t remove existing qualifiers and only add new ones. Our copy is different and instead fully replaces qualifiers, because this behavior is consistent with data copy.

#include <actl/meta/qualifiers/copy.hpp>

template<typename Target, typename Source> using ac::copy_const_t = typename copy_const<Target, Source>::type¶

template<typename Target, typename Source> using ac::copy_volatile_t = typename copy_volatile<Target, Source>::type¶

template<typename Target, typename Source> using ac::copy_cv_t = typename copy_cv<Target, Source>::type¶

template<typename Target, typename Source> using ac::copy_reference_t = typename copy_reference<Target, Source>::type¶

template<typename Target, typename Source> using ac::copy_cvref_t = typename copy_cvref<Target, Source>::type¶

See tests at tests/meta/qualifiers/copy.cpp

Inner qualifiers modification¶

Traits that add or remove type qualifiers. If the type is a reference, then the referenced type is modified.

Trait name	Non-reference	Reference
Input type	`int`	`int&`
`add_inner_const_t`	`int const`	`int const&`
`add_inner_volatile_t`	`int volatile`	`int volatile&`
`add_inner_cv_t`	`int const volatile`	`int const volatile&`

Trait name	Non-reference	Reference
Input type	`int const volatile`	`int const volatile&`
`remove_inner_const_t`	`int volatile`	`int volatile&`
`remove_inner_volatile_t`	`int const`	`int const&`
`remove_inner_cv_t`	`int`	`int&`

#include <actl/meta/qualifiers/inner.hpp>

template<typename T> using ac::add_inner_const_t = typename add_inner_const<T>::type¶

template<typename T> using ac::remove_inner_const_t = typename remove_inner_const<T>::type¶

template<typename T> using ac::add_inner_volatile_t = typename add_inner_volatile<T>::type¶

template<typename T> using ac::remove_inner_volatile_t = typename remove_inner_volatile<T>::type¶

template<typename T> using ac::add_inner_cv_t = typename add_inner_cv<T>::type¶

template<typename T> using ac::remove_inner_cv_t = typename remove_inner_cv<T>::type¶

See tests at tests/meta/qualifiers/inner.cpp