Add initial test.

Author: tinko92

extensions/test/Jamfile

@@ -28,3 +28,4 @@ build-project gis ;
 build-project iterators ;
 build-project nsphere ;
 build-project triangulation ;
+build-project generic_robust_predicates ;

extensions/test/generic_robust_predicates/Jamfile

@@ -0,0 +1,11 @@
+# Boost.Geometry (aka GGL, Generic Geometry Library)
+#
+# Use, modification and distribution is subject to 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)
+
+test-suite boost-geometry-extensions-generic_robust_predicates
+    :
+    [ run approximate.cpp ]
+    ;
+

extensions/test/generic_robust_predicates/approximate.cpp

@@ -0,0 +1,55 @@
+// Boost.Geometry (aka GGL, Generic Geometry Library)
+// Unit Test
+
+// Copyright (c) 2020 Tinko Bartels, Berlin, Germany.
+
+// Contributed and/or modified by Tinko Bartels,
+//   as part of Google Summer of Code 2020 program.
+
+// Use, modification and distribution is subject to 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)
+
+#include <array>
+
+#include <geometry_test_common.hpp>
+
+#include <boost/geometry/extensions/generic_robust_predicates/strategies/cartesian/detail/approximate.hpp>
+#include <boost/geometry/extensions/generic_robust_predicates/strategies/cartesian/detail/expression_tree.hpp>
+
+namespace p = boost::geometry::detail::generic_robust_predicates;
+
+template <typename CalculationType>
+void test_all()
+{
+    using ct = CalculationType;
+    ct r1 = p::approximate_value<p::sum<p::_1, p::_2>, ct>(
+            std::array<ct, 2>{1.0, 2.0});
+    BOOST_CHECK_EQUAL(3.0, r1);
+    ct r2 = p::approximate_value<p::max<p::abs<p::_1>, p::abs<p::_2>>, ct>(
+            std::array<ct, 2>{-10.0, 2.0});
+    BOOST_CHECK_EQUAL(10.0, r2);
+
+    using expression = p::product
+        <
+            p::difference<p::_1, p::_2>,
+            p::difference<p::_3, p::_4>
+        >;
+    using evals = p::post_order<expression>;
+    std::array<ct, boost::mp11::mp_size<evals>::value> r;
+    std::array<ct, 4> input {5.0, 3.0, 2.0, 8.0};
+    p::approximate_interim<evals, evals, ct>(r, input);
+    ct r3 = p::get_approx<evals, typename expression::left, ct>(r, input);
+    BOOST_CHECK_EQUAL(2.0, r3);
+    ct r4 = p::get_approx<evals, typename expression::right, ct>(r, input);
+    BOOST_CHECK_EQUAL(-6.0, r4);
+    ct r5 = p::get_approx<evals, expression, ct>(r, input);
+    BOOST_CHECK_EQUAL(-12.0, r5);
+}
+
+
+int test_main(int, char* [])
+{
+    test_all<double>();
+    return 0;
+}