Specialize operator= when RHS is chunked

Author: davidbrochart

include/xtensor/xchunked_view.hpp

@@ -19,6 +19,21 @@
 namespace xt
 {
 
+    // SFINAE test if chunked
+    template <typename T>
+    class has_chunks
+    {
+    private:
+        typedef char YesType[1];
+        typedef char NoType[2];
+
+        template <typename C> static YesType& test(decltype(&C::chunk_shape));
+        template <typename C> static NoType& test(...);
+
+    public:
+        enum { value = sizeof(test<T>(0)) == sizeof(YesType) };
+    };
+
     /*****************
      * xchunked_view *
      *****************/
@@ -48,7 +63,10 @@ namespace xt
         xchunked_view(OE&& e, S&& chunk_shape);
 
         template <class OE>
-        xchunked_view<E>& operator=(const OE& e);
+        typename std::enable_if<!has_chunks<OE>::value, xchunked_view<E>&>::type operator=(const OE& e);
+
+        template <class OE>
+        typename std::enable_if<has_chunks<OE>::value, xchunked_view<E>&>::type operator=(const OE& e);
 
         size_type dimension() const noexcept;
         const shape_type& shape() const noexcept;
@@ -114,7 +132,7 @@ namespace xt
 
     template <class E>
     template <class OE>
-    xchunked_view<E>& xchunked_view<E>::operator=(const OE& e)
+    typename std::enable_if<!has_chunks<OE>::value, xchunked_view<E>&>::type xchunked_view<E>::operator=(const OE& e)
     {
         for (auto it = chunk_begin(); it != chunk_end(); it++)
         {
@@ -124,6 +142,30 @@ namespace xt
         return *this;
     }
 
+    template <class E>
+    template <class OE>
+    typename std::enable_if<has_chunks<OE>::value, xchunked_view<E>&>::type xchunked_view<E>::operator=(const OE& e)
+    {
+        for (auto it1 = chunk_begin(), it2 = e.chunks().begin(); it1 != chunk_end(); it1++, it2++)
+        {
+            auto el1 = *it1;
+            auto el2 = *it2;
+            auto lhs_shape = el1.shape();
+            if (lhs_shape != el2.shape())
+            {
+                xstrided_slice_vector esv(el2.dimension());  // element slice in edge chunk
+                std::transform(lhs_shape.begin(), lhs_shape.end(), esv.begin(),
+                               [](auto size) { return range(0, size); });
+                noalias(el1) = strided_view(el2, esv);
+            }
+            else
+            {
+                noalias(el1) = el2;
+            }
+        }
+        return *this;
+    }
+
     template <class E>
     inline auto xchunked_view<E>::dimension() const noexcept -> size_type
     {