std::meta::add_const, std::meta::add_volatile, std::meta::add_cv
Defined in header <meta> | ||
|---|---|---|
consteval std::meta::info add_const( std::meta::info r ); | (1) | (since C++26) |
consteval std::meta::info add_volatile( std::meta::info r ); | (2) | (since C++26) |
consteval std::meta::info add_cv( std::meta::info r ); | (3) | (since C++26) |
Returns a reflection of a type T, represented by r, with the cv-qualifier added. If r represents a function, a reference, or already has this qualifier, r is returned unmodified.
1) Adds const qualifier.
Equivalent to
return std::meta::dealias(^^std::add_const_t<T>);.
2) Adds volatile qualifier.
Equivalent to
return std::meta::dealias(^^std::add_volatile_t<T>);.
3) Adds both const and volatile qualifiers.
Equivalent to
return std::meta::dealias(^^std::add_cv_t<T>);.Parameters
| r | - | a reflection value |
Return value
A reflection of the type represented by r with added topmost cv-qualifiers appropriately.
Exceptions
Throws std::meta::exception if r does not represent a type or type alias.
Example
#include <meta>
#include <print>
#include <source_location>
static_assert
(""
and (add_const(^^int) == ^^const int)
and (add_volatile(^^int) == ^^volatile int)
and (add_cv(^^int) == ^^const volatile int)
and (add_cv(^^const volatile int) == ^^const volatile int)
// add_cv only works on types, not on pointers
and (add_cv(^^int*) != ^^const volatile int*)
and (add_cv(^^int*) == ^^int* const volatile)
and (add_cv(^^const volatile int*) == ^^const volatile int* const volatile)
);
inline void fun_name(std::source_location src = std::source_location::current())
{
return std::println("{}", src.function_name());
}
struct S
{
void fun() { fun_name(); }
void fun() const { fun_name(); }
void fun() volatile { fun_name(); }
void fun() const volatile { fun_name(); }
};
int main()
{
S{}.fun();
typename [:add_const(^^S):]{}.fun();
typename [:add_volatile(^^S):]{}.fun();
typename [:add_cv(^^S):]{}.fun();
}
Possible output:
void S::fun() void S::fun() const void S::fun() volatile void S::fun() const volatile
See also
|
(C++26) | checks if reflection represents a const type or a function type with const qualifier (function) |
|
(C++26) | checks if reflection represents a volatile type or a function type with volatile qualifier (function) |
|
(C++26)(C++26)(C++26) | removes const and/or volatile qualifiers from reflected type (function) |
|
(C++17) | obtains a reference to const to its argument (function template) |
|
(C++23) | converts a view into a constant_range(class template) (range adaptor object) |
|
(C++11)(C++11)(C++11) | adds const and/or volatile qualifiers to the given type (class template) |
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https://en.cppreference.com/cpp/meta/add_cv
