this now works, TODO: the shared_edge_indices returns the indices in …

…the _first_parameter_ if the second parameter is a subsban, the indices should be offset by the starting index. This is potentially dangerous and needs to be thought carefully.

include/bits/geometry/box.hpp

@@ -333,12 +333,51 @@ template <size_t N>
 Box<N> shared_edge(const Box<N>&                   b1,
                    const Box<N>&                   b2,
                    const std::array<index_type, N> dir) {
+
+
+    std::array<index_type, N> beg{};
+    std::array<index_type, N> end{};
+
+
+
+   if (have_shared_edges(b1, b2, dir)){
+
+        for (size_t i = 0; i < N; ++i){
+
+            if (dir[i] == 1 && (b1.end[i] == b2.end[i])){
+                end[i] = b1.end[i];
+                beg[i] = end[i] - 1;
+            }
+            if (dir[i] == -1 && (b1.begin[i] == b2.begin[i])){
+                beg[i] = b1.begin[i];
+                end[i] = beg[i] + 1;
+            }
+
+            if (dir[i] == 0){
+                beg[i] = std::max(b1.begin[i], b2.begin[i]);
+                end[i] = std::min(b1.end[i], b2.end[i]);
+            }
+
+
+        }
+
+   }
+
+    return Box<N>(beg, end);
+
+
+    /*
+
+
     if (have_shared_edges(b1, b2, dir)) {
+
+
         return intersection(get_edge(b1, dir), get_edge(b2, dir));
     }
     std::array<index_type, N> beg{};
     std::array<index_type, N> end{};
     return Box<N>(beg, end);
+    */
 }
 
 /// @brief Given two boxes and a direction vector, determines the shared edge

test/test_geometry.cpp

@@ -349,6 +349,16 @@ TEST_CASE("Test box") {
             CHECK(r1 == Box<2>({0,0}, {2,1}));
         }
 
+        SECTION("Test 3"){
+
+            const Box<2> domain({0,0}, {3,4});
+            const Box<2> sub({0, 2}, {3,4});
+
+            auto r1 = shared_edge(domain, sub, {0, 1});
+            CHECK(r1 == Box<2>({0,3}, {3, 4}));
+
+        }
+
     }
 
 
@@ -429,37 +439,59 @@ TEST_CASE("Test box") {
 
         }
 
-        /*
+        SECTION("Bug 1"){
+            const Box<2> domain({0,0}, {3,4});
+            const Box<2> sub({0, 2}, {3,4});
+            std::vector<int> data(flat_size(domain.get_extent()), 0);
+            auto span = make_span(data, domain.get_extent());
+            for (auto [j, i] : shared_edge_indices(domain, sub, {0, 1})){
+                    span(j, i) = 1;
+            }
+            CHECK
+            (
+                data ==
+                std::vector<int> {0,0,0,1,
+                                    0,0,0,1,
+                                    0,0,0,1}
+            );
+        }
+
+
+
         SECTION("boundary_loops"){
 
             auto domain = Box<2>{{0,0}, {3, 4}};
             auto topo = decompose(domain, 3, {false, false});
-            std::vector<int> data(flat_size(domain.get_extent()), 0);
 
-            auto bigspan = make_span(data, domain.get_extent());
+            SECTION("dir {0, 1}"){
+                std::vector<int> data(flat_size(domain.get_extent()), 0);
 
-            for (auto box : topo.get_boxes()){
+                auto bigspan = make_span(data, domain.get_extent());
 
-                auto subspan = make_subspan(bigspan, box.box.begin, box.box.end);
+                for (auto box : topo.get_boxes()){
 
-                auto indices = shared_edge_indices(domain, box.box, {0, 1});
+                    auto subspan = make_subspan(bigspan, box.box.begin, box.box.end);
+
+                    //auto indices = shared_edge_indices(domain, box.box, {0, 1});
+
+                    for (auto [j,i] : shared_edge_indices(domain, box.box, {0, 1}))
+                    {
+                        bigspan(j,i) = 1;
+                    }
 
-                for (auto [j,i] : indices){
-                    subspan(j,i) = 1;
                 }
 
+                CHECK
+                (
+                    data ==
+                    std::vector<int> {0,0,0,1,
+                                      0,0,0,1,
+                                      0,0,0,1}
+                );
             }
+        }
 
-            CHECK
-            (
-                data ==
-                std::vector<int> {0,0,0,1,
-                                    0,0,0,1,
-                                    0,0,0,1}
-            );
 
-        }
-        */
     }
 
 }