Add examples/point2.cpp

examples/Jamfile.v2

@@ -7,3 +7,4 @@ run books.cpp ;
 run point.cpp ;
 run portable.cpp ;
 run template.cpp : : : <toolset>msvc-8.0:<build>no ;
+run point2.cpp ;

examples/point2.cpp

@@ -0,0 +1,65 @@
+
+// Copyright 2005 Daniel James.
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+// Force use of assert.
+#if defined(NDEBUG)
+#undef NDEBUG
+#endif
+
+#include <boost/container_hash/hash.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/describe/operators.hpp>
+#include <cassert>
+
+// This example illustrates how to use Boost.Describe to obtain
+// automatic boost::hash support. For full details see the hash
+// tutorial.
+
+#if defined(BOOST_DESCRIBE_CXX14)
+
+class point
+{
+    int x;
+    int y;
+
+    BOOST_DESCRIBE_CLASS(point, (), (), (), (x, y))
+
+public:
+
+    point() : x(0), y(0) {}
+    point(int x, int y) : x(x), y(y) {}
+};
+
+using boost::describe::operators::operator==;
+using boost::describe::operators::operator!=;
+
+int main()
+{
+    boost::hash<point> point_hasher;
+
+    point p1(0, 0);
+    point p2(1, 2);
+    point p3(4, 1);
+    point p4 = p1;
+
+    assert(point_hasher(p1) == point_hasher(p4));
+
+    // These tests could legally fail, but if they did it'd be a pretty bad
+    // hash function.
+    assert(point_hasher(p1) != point_hasher(p2));
+    assert(point_hasher(p1) != point_hasher(p3));
+}
+
+#else
+
+#include <cstdio>
+
+int main()
+{
+    std::puts( "This example requires C++14." );
+}
+
+#endif