1 // Boost.Geometry
2 
3 // Copyright (c) 2021, Oracle and/or its affiliates.
4 
5 // Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
6 
7 // Licensed under the Boost Software License version 1.0.
8 // http://www.boost.org/users/license.html
9 
10 #ifndef BOOST_GEOMETRY_CORE_VISIT_HPP
11 #define BOOST_GEOMETRY_CORE_VISIT_HPP
12 
13 #include <utility>
14 
15 #include <boost/range/value_type.hpp>
16 
17 #include <boost/geometry/core/static_assert.hpp>
18 #include <boost/geometry/util/type_traits_std.hpp>
19 
20 
21 namespace boost { namespace geometry { namespace traits
22 {
23 
24 // TODO: Alternatives:
25 // - free function
26 //    template <typename Visitor, typename ...Variants>
27 //    auto visit(Visitor &&, Variants && ...) {}
28 //
29 // - additional Enable tparam
30 //    template <bool Enable, typename ...DynamicGeometries>
31 //    struct visit {};
32 
33 template <typename ...DynamicGeometries>
34 struct visit
35 {
36     BOOST_GEOMETRY_STATIC_ASSERT_FALSE(
37         "Not implemented for these DynamicGeometries types.",
38         DynamicGeometries...);
39 };
40 
41 // By default call 1-parameter visit for each geometry
42 template <typename DynamicGeometry1, typename DynamicGeometry2>
43 struct visit<DynamicGeometry1, DynamicGeometry2>
44 {
45     template <typename Function, typename Variant1, typename Variant2>
applyboost::geometry::traits::visit46     static void apply(Function && function, Variant1 && variant1, Variant2 && variant2)
47     {
48         visit<util::remove_cref_t<Variant1>>::apply([&](auto && g1)
49         {
50             using ref1_t = decltype(g1);
51             visit<util::remove_cref_t<Variant2>>::apply([&](auto && g2)
52             {
53                 function(std::forward<ref1_t>(g1),
54                          std::forward<decltype(g2)>(g2));
55             }, std::forward<Variant2>(variant2));
56         }, std::forward<Variant1>(variant1));
57     }
58 };
59 
60 // By default treat GeometryCollection as a range of DynamicGeometries
61 template <typename GeometryCollection>
62 struct iter_visit
63 {
64     template <typename Function, typename Iterator>
applyboost::geometry::traits::iter_visit65     static void apply(Function && function, Iterator iterator)
66     {
67         using value_t = typename boost::range_value<GeometryCollection>::type;
68         using reference_t = typename std::iterator_traits<Iterator>::reference;
69         visit<value_t>::apply(std::forward<Function>(function),
70                               std::forward<reference_t>(*iterator));
71     }
72 };
73 
74 }}} // namespace boost::geometry::traits
75 
76 #endif // BOOST_GEOMETRY_CORE_VISIT_HPP
77