Add decay_tuple.

Author: evoskuil

include/bitcoin/system/typelets.hpp

@@ -151,6 +151,18 @@ template <typename Larger, typename Smaller, size_t Lanes = one,
     ////std::enable_if_t<Lanes <= (max_size_t / size_of<Smaller>()), bool> = true>
 constexpr size_t capacity = size_of<Larger>() / (Lanes * size_of<Smaller>());
 
+/// std::tuple decay elements.
+/// ---------------------------------------------------------------------------
+
+template <typename Tuple>
+struct decay_tuple;
+
+template <typename ...Args>
+struct decay_tuple<std::tuple<Args...>>
+{
+    using type = std::tuple<std::decay_t<Args>...>;
+};
+
 /// uintx_t detection.
 /// ---------------------------------------------------------------------------
 

test/typelets.cpp

@@ -417,6 +417,55 @@ static_assert(size_of<std_array<const volatile std_array<std_array<uint32_t, 42>
 static_assert(size_of<std_array<std_array<const volatile std_array<uint32_t, 42>, 24>, 8>>() == sizeof(uint32_t) * 42 * 24 * 8);
 static_assert(size_of<const volatile std_array<const volatile std_array<const volatile std_array<uint32_t, 42>, 24>, 8>&>() == sizeof(uint32_t) * 42 * 24 * 8);
 
+
+// std::tuple decay elements.
+// ----------------------------------------------------------------------------
+// is_same_type decays individual types (but not tuple elements).
+
+using test_tuple = std::tuple<int&, bool&&, const std::string&>;
+static_assert( is_same_type<decay_tuple<test_tuple>, decay_tuple<test_tuple>>);
+static_assert(!is_same_type<test_tuple, decay_tuple<test_tuple>>);
+static_assert(!is_same_type<decay_tuple<test_tuple>, test_tuple>);
+
+static_assert(!std::is_same_v<std::tuple_element<0, test_tuple>::type, int>);
+static_assert(!std::is_same_v<std::tuple_element<1, test_tuple>::type, bool>);
+static_assert(!std::is_same_v<std::tuple_element<2, test_tuple>::type, std::string>);
+
+static_assert(!std::is_same_v<std::tuple_element<0, test_tuple>::type, const int>);
+static_assert(!std::is_same_v<std::tuple_element<1, test_tuple>::type, const bool>);
+static_assert(!std::is_same_v<std::tuple_element<2, test_tuple>::type, const std::string>);
+
+static_assert( std::is_same_v<std::tuple_element<0, test_tuple>::type, int&>);
+static_assert(!std::is_same_v<std::tuple_element<1, test_tuple>::type, bool&>);
+static_assert(!std::is_same_v<std::tuple_element<2, test_tuple>::type, std::string&>);
+
+static_assert(!std::is_same_v<std::tuple_element<0, test_tuple>::type, int&&>);
+static_assert( std::is_same_v<std::tuple_element<1, test_tuple>::type, bool&&>);
+static_assert(!std::is_same_v<std::tuple_element<2, test_tuple>::type, std::string&&>);
+
+using normal_test_tuple = std::tuple<int, bool, std::string>;
+using decayed_test_tuple = decay_tuple<test_tuple>::type;
+static_assert(is_same_type<normal_test_tuple, decayed_test_tuple>);
+
+static_assert(std::is_same_v<std::tuple_element<0, decayed_test_tuple>::type, int>);
+static_assert(std::is_same_v<std::tuple_element<1, decayed_test_tuple>::type, bool>);
+static_assert(std::is_same_v<std::tuple_element<2, decayed_test_tuple>::type, std::string>);
+
+static_assert(!std::is_same_v<std::tuple_element<0, decayed_test_tuple>::type, const int>);
+static_assert(!std::is_same_v<std::tuple_element<1, decayed_test_tuple>::type, const bool>);
+static_assert(!std::is_same_v<std::tuple_element<2, decayed_test_tuple>::type, const std::string>);
+
+static_assert(!std::is_same_v<std::tuple_element<0, decayed_test_tuple>::type, int&>);
+static_assert(!std::is_same_v<std::tuple_element<1, decayed_test_tuple>::type, bool&>);
+static_assert(!std::is_same_v<std::tuple_element<2, decayed_test_tuple>::type, std::string&>);
+
+static_assert(!std::is_same_v<std::tuple_element<0, decayed_test_tuple>::type, int&&>);
+static_assert(!std::is_same_v<std::tuple_element<1, decayed_test_tuple>::type, bool&&>);
+static_assert(!std::is_same_v<std::tuple_element<2, decayed_test_tuple>::type, std::string&&>);
+
+// is_uintx
+// ----------------------------------------------------------------------------
+
 static_assert(is_uintx<uint5_t>);
 static_assert(is_uintx<uint11_t>);
 static_assert(is_uintx<uint48_t>);