[type_traits] add copy_cv

Author: iboB

include/itlib/type_traits.hpp

@@ -1,4 +1,4 @@
-// itlib-type_traits v1.02
+// itlib-type_traits v1.03
 //
 // Additional helper type traits extending the standard <type_traits>
 //
@@ -28,6 +28,7 @@
 //
 //                  VERSION HISTORY
 //
+//  1.03 (2025-12-15) Add copy_cv
 //  1.02 (2023-11-27) Added is_noop_convertible
 //  1.01 (2023-03-10) Added type_identity
 //  1.00 (2020-12-28) First pulic release
@@ -89,6 +90,14 @@ struct is_noop_convertible {
         ;
 };
 
+template <typename To, typename From>
+struct copy_cv {
+    using type = typename std::conditional<std::is_const<From>::value,
+        typename std::conditional<std::is_volatile<From>::value, const volatile To, const To>::type,
+        typename std::conditional<std::is_volatile<From>::value, volatile To, To>::type
+    >::type;
+};
+
 #if __cplusplus >= 201700
 template <template <typename...> class Template, typename Type>
 inline constexpr bool is_instantiation_of_v = is_instantiation_of<Template, Type>::value;
@@ -98,6 +107,9 @@ using type_identity_t = typename type_identity<T>::type;
 
 template <typename From, typename To>
 inline constexpr bool is_noop_convertible_v = is_noop_convertible<From, To>::value;
+
+template <typename To, typename From>
+using copy_cv_t = typename copy_cv<To, From>::type;
 #endif
 
 }

test/t-type_traits-11.cpp

@@ -61,3 +61,26 @@ TEST_CASE("is_noop_convertible") {
     CCHECK_FALSE(itlib::is_noop_convertible<int8_t, bool>::value);
     CCHECK_FALSE(itlib::is_noop_convertible<int8_t, const bool>::value);
 }
+
+TEST_CASE("copy_cv") {
+    CCHECK(std::is_same<
+        itlib::copy_cv<int, const volatile float>::type,
+        const volatile int
+    >::value);
+    CCHECK(std::is_same<
+        itlib::copy_cv<const int, volatile float>::type,
+        volatile const int
+    >::value);
+    CCHECK(std::is_same<
+        itlib::copy_cv<volatile int, const float>::type,
+        const volatile int
+    >::value);
+    CCHECK(std::is_same<
+        itlib::copy_cv<const volatile int, float>::type,
+        const volatile int
+    >::value);
+    CCHECK(std::is_same<
+        itlib::copy_cv<int, float>::type,
+        int
+    >::value);
+}

test/t-type_traits-17.cpp

@@ -53,3 +53,15 @@ TEST_CASE("is_noop_convertible") {
     CCHECK_FALSE(itlib::is_noop_convertible_v<void*, float>);
     CCHECK_FALSE(itlib::is_noop_convertible_v<void*, double>);
 }
+
+
+TEST_CASE("copy_cv") {
+    using T1 = itlib::copy_cv_t<float, const volatile int>;
+    CCHECK(std::is_same_v<T1, const volatile float>);
+    using T2 = itlib::copy_cv_t<double, int>;
+    CCHECK(std::is_same_v<T2, double>);
+    using T3 = itlib::copy_cv_t<long, volatile char>;
+    CCHECK(std::is_same_v<T3, volatile long>);
+    using T4 = itlib::copy_cv_t<unsigned short, const short>;
+    CCHECK(std::is_same_v<T4, const unsigned short>);
+}