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Add CGAL::is_convertible_without_narrowing 

... and `CGAL::cpp20::type_identity`.
This commit is contained in:
Laurent Rineau 2024-04-23 13:33:07 +02:00
parent 1d5851e013
commit ca1f11d715
2 changed files with 43 additions and 9 deletions
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26
STL_Extension/include/CGAL/type_traits.h
View File

@ -29,6 +29,12 @@ struct is_same_or_derived :
namespace cpp20 {
template<class T>
struct type_identity { using type = T; };
template<class T>
using type_identity_t = typename type_identity<T>::type;
template< class T >
struct remove_cvref {
typedef std::remove_cv_t<std::remove_reference_t<T>> type;
@ -39,6 +45,26 @@ namespace cpp20 {
} // end namespace cpp20
namespace details {
template <typename From, typename To, typename = void>
struct is_convertible_without_narrowing : std::false_type
{};
template <typename From, typename To>
struct is_convertible_without_narrowing<From,
To,
std::void_t<decltype(cpp20::type_identity_t<To[]>{std::declval<From>()})>>
: std::is_convertible<From, To>
{};
}
template <typename From, typename To>
struct is_convertible_without_narrowing : details::is_convertible_without_narrowing<From, To>
{};
template <typename From, typename To>
inline constexpr bool is_convertible_without_narrowing_v = is_convertible_without_narrowing<From, To>::value;
} // end namespace CGAL
#endif // CGAL_TYPE_TRAITS_H

26
STL_Extension/test/STL_Extension/test_type_traits.cpp
View File

@ -18,14 +18,22 @@ struct B : public A {};
typedef A C;
int main() {
assert( ( ::CGAL::is_same_or_derived< A,A >::value == 1 ) );
assert( ( ::CGAL::is_same_or_derived< A,B >::value == 1 ) );
assert( ( ::CGAL::is_same_or_derived< B,A >::value == 0 ) );
assert( ( ::CGAL::is_same_or_derived< B,B >::value == 1 ) );
assert( ( ::CGAL::is_same_or_derived< A,C >::value == 1 ) );
assert( ( ::CGAL::is_same_or_derived< B,C >::value == 0 ) );
assert( ( ::CGAL::is_same_or_derived< C,C >::value == 1 ) );
assert( ( ::CGAL::is_same_or_derived< C,A >::value == 1 ) );
assert( ( ::CGAL::is_same_or_derived< C,B >::value == 1 ) );
static_assert( ( ::CGAL::is_same_or_derived< A,A >::value == 1 ) );
static_assert( ( ::CGAL::is_same_or_derived< A,B >::value == 1 ) );
static_assert( ( ::CGAL::is_same_or_derived< B,A >::value == 0 ) );
static_assert( ( ::CGAL::is_same_or_derived< B,B >::value == 1 ) );
static_assert( ( ::CGAL::is_same_or_derived< A,C >::value == 1 ) );
static_assert( ( ::CGAL::is_same_or_derived< B,C >::value == 0 ) );
static_assert( ( ::CGAL::is_same_or_derived< C,C >::value == 1 ) );
static_assert( ( ::CGAL::is_same_or_derived< C,A >::value == 1 ) );
static_assert( ( ::CGAL::is_same_or_derived< C,B >::value == 1 ) );
static_assert( CGAL::is_convertible_without_narrowing_v<int, int> );
static_assert( ! CGAL::is_convertible_without_narrowing_v<int, signed char> );
static_assert( CGAL::is_convertible_without_narrowing_v<signed char, int> );
static_assert( ! CGAL::is_convertible_without_narrowing_v<int, double> );
static_assert( CGAL::is_convertible_without_narrowing_v<float, double> );
static_assert( ! CGAL::is_convertible_without_narrowing_v<double, float> );
static_assert( ! CGAL::is_convertible_without_narrowing_v<A, int> );
return 0;
}