optional support for c++20

src/polymesh/cursors.hh

@@ -24,6 +24,10 @@ struct primitive_index
     bool is_invalid() const { return value < 0; }
     static const index_t invalid;
 
+#ifdef POLYMESH_CPP20
+    bool operator==(primitive_index const&) const = default;
+    auto operator<=>(primitive_index const&) const = default;
+#else
     bool operator<(index_t const& rhs) const { return value < rhs.value; }
     bool operator<=(index_t const& rhs) const { return value <= rhs.value; }
     bool operator>(index_t const& rhs) const { return value > rhs.value; }
@@ -32,6 +36,7 @@ struct primitive_index
     bool operator!=(index_t const& rhs) const { return value != rhs.value; }
     bool operator==(handle_t const& rhs) const { return value == rhs.idx.value; }
     bool operator!=(handle_t const& rhs) const { return value != rhs.idx.value; }
+#endif
 
     explicit operator int() const { return value; }
 
@@ -73,10 +78,14 @@ struct primitive_handle
     primitive_handle() = default;
     primitive_handle(Mesh const* mesh, index_t idx) : mesh(mesh), idx(idx) {}
 
-    bool operator==(index_t const& rhs) const { return idx == rhs; }
-    bool operator!=(index_t const& rhs) const { return idx != rhs; }
+#ifdef POLYMESH_CPP20
+    bool operator==(primitive_handle const&) const = default;
+#else
     bool operator==(handle_t const& rhs) const { return mesh == rhs.mesh && idx == rhs.idx; }
     bool operator!=(handle_t const& rhs) const { return mesh != rhs.mesh || idx != rhs.idx; }
+#endif
+    bool operator==(index_t const& rhs) const { return idx == rhs; }
+    bool operator!=(index_t const& rhs) const { return idx != rhs; }
 
     explicit operator int() const { return (int)idx; }
     operator index_t() const { return idx; }

src/polymesh/iterators.hh

@@ -149,7 +149,7 @@ struct primitive_circulator : smart_iterator<this_t>
 
     primitive_circulator(halfedge_handle h, bool at_begin = true) : handle(h), end(h), at_begin(at_begin) {}
 
-    bool is_valid() const { return at_begin || handle != end; }
+    bool is_valid() const { return at_begin || handle.idx != end; }
 };
 
 struct face_vertex_circulator : primitive_circulator<face_vertex_circulator>
@@ -195,7 +195,7 @@ struct face_face_circulator : primitive_circulator<face_face_circulator>
         do // skip invalid faces
         {
             handle = handle.next();
-        } while (handle != end && handle.opposite_face().is_invalid());
+        } while (handle.idx != end && handle.opposite_face().is_invalid());
         at_begin = false;
     }
 };
@@ -243,7 +243,7 @@ struct vertex_face_circulator : primitive_circulator<vertex_face_circulator>
         do // skip invalid faces
         {
             handle = handle.prev().opposite();
-        } while (handle != end && handle.face().is_invalid());
+        } while (handle.idx != end && handle.face().is_invalid());
         at_begin = false;
     }
 };

src/polymesh/macros.hh

@@ -17,6 +17,10 @@
 #error "Unknown compiler"
 #endif
 
+#if __cplusplus >= 202002L
+#define POLYMESH_CPP20
+#endif
+
 
 // =========
 // compiler specific builtins

src/polymesh/tmp.hh

@@ -3,6 +3,12 @@
 #include <cstddef>
 #include <utility>
 
+#include <polymesh/macros.hh>
+
+#ifdef POLYMESH_CPP20
+#include <compare>
+#endif
+
 namespace polymesh
 {
 // small template metaprogramming