Implement N3672, optional<T>.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@189772 91177308-0d34-0410-b5e6-96231b3b80d8

test/utilities/optional/optional.relops/less_than.pass.cpp

@@ -0,0 +1,86 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <optional>
+
+// template <class T> constexpr bool operator< (const optional<T>& x, const optional<T>& y);
+
+#include <optional>
+
+#if _LIBCPP_STD_VER > 11
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+namespace std
+{
+
+template <>
+struct less<X>
+{
+    constexpr
+    bool
+    operator()(const X& x, const X& y) const
+    {
+        return x.i_ < y.i_;
+    }
+};
+
+}
+
+#endif
+
+int main()
+{
+#if _LIBCPP_STD_VER > 11
+    {
+    typedef std::optional<X> O;
+    
+    constexpr O o1;     // disengaged
+    constexpr O o2;     // disengaged
+    constexpr O o3{1};  // engaged
+    constexpr O o4{2};  // engaged
+    constexpr O o5{1};  // engaged
+    
+    static_assert ( !(o1 < o1), "" );
+    static_assert ( !(o1 < o2), "" );
+    static_assert (   o1 < o3 , "" );
+    static_assert (   o1 < o4 , "" );
+    static_assert (   o1 < o5 , "" );
+
+    static_assert ( !(o2 < o1), "" );
+    static_assert ( !(o2 < o2), "" );
+    static_assert (   o2 < o3 , "" );
+    static_assert (   o2 < o4 , "" );
+    static_assert (   o2 < o5 , "" );
+
+    static_assert ( !(o3 < o1), "" );
+    static_assert ( !(o3 < o2), "" );
+    static_assert ( !(o3 < o3), "" );
+    static_assert (   o3 < o4 , "" );
+    static_assert ( !(o3 < o5), "" );
+
+    static_assert ( !(o4 < o1), "" );
+    static_assert ( !(o4 < o2), "" );
+    static_assert ( !(o4 < o3), "" );
+    static_assert ( !(o4 < o4), "" );
+    static_assert ( !(o4 < o5), "" );
+
+    static_assert ( !(o5 < o1), "" );
+    static_assert ( !(o5 < o2), "" );
+    static_assert ( !(o5 < o3), "" );
+    static_assert (   o5 < o4 , "" );
+    static_assert ( !(o5 < o5), "" );
+    }
+#endif
+}