Add tombstone_traits tests

Author: davidstone

source/bounded/CMakeLists.txt

@@ -130,6 +130,7 @@ target_sources(bounded_test PRIVATE
 		test/conditional.cpp
 		test/stream.cpp
 		test/to_integer.cpp
+		test/tombstone_traits.cpp
 )
 
 target_link_libraries(bounded_test PUBLIC

source/bounded/test/tombstone_traits.cpp

@@ -0,0 +1,69 @@
+// Copyright David Stone 2024.
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+export module bounded.test.tombstone_traits;
+
+import bounded.arithmetic.unary_minus;
+import bounded.comparison;
+import bounded.integer;
+import bounded.literal;
+import bounded.tombstone_traits;
+
+namespace {
+using namespace bounded::literal;
+
+struct a {
+	int m;
+};
+
+struct b {
+	constexpr b():
+		m(1)
+	{
+	}
+	a m;
+private:
+	constexpr explicit b(bounded::tombstone_tag, auto const make):
+		m(make())
+	{
+	}
+	friend bounded::tombstone_traits_composer<&b::m>;
+};
+
+} // namespace
+
+template<>
+struct bounded::tombstone_traits<a> {
+	static constexpr auto spare_representations = 1_bi;
+	static constexpr auto make(bounded::constant_t<0>) noexcept -> a {
+		return a(0);
+	}
+	static constexpr auto index(a const & value) noexcept -> bounded::integer<-1, 0> {
+		if (value.m == 0) {
+			return 0_bi;
+		}
+		return -1_bi;
+	}
+};
+
+template<>
+struct bounded::tombstone_traits<b> : bounded::tombstone_traits_composer<&b::m> {
+};
+
+namespace {
+
+using a_traits = bounded::tombstone_traits<a>;
+static_assert(a_traits::spare_representations == 1_bi);
+static_assert(a_traits::make(0_bi).m == 0);
+static_assert(a_traits::index(a(0)) == 0_bi);
+static_assert(a_traits::index(a(1)) == -1_bi);
+
+using b_traits = bounded::tombstone_traits<b>;
+static_assert(b_traits::spare_representations == 1_bi);
+static_assert(b_traits::make(0_bi).m.m == 0);
+static_assert(b_traits::index(b_traits::make(0_bi)) == 0_bi);
+static_assert(b_traits::index(b()) == -1_bi);
+
+} // namespace