Is there a way to use c 20s concepts to check that a value meets some requirements?
Lets say I am writing some sort of container that uses paging and i want to make the page size a template parameter.
template<typename Type, std::size_t PageSize>
class container;
I could use a static assert with a constexpr function to check if PageSize
is a power of two inside the class body.
But is there a way to use the new concepts to restrain PageSize
?
CodePudding user response:
C 20 introduced std::has_single_bit
to check if x
is an integral power of two, so you can use requires
expression to constrain PageSize
.
#include <bit>
template<typename Type, std::size_t PageSize>
requires (std::has_single_bit(PageSize))
class container { };
CodePudding user response:
The easiest way would be to constrain the template parameters of the class.
constexpr bool is_power_of_two(std::size_t x) { /*... */ }
template<typename Type, std::size_t PageSize>
requires ( is_power_of_two(PageSize) )
class container;