making adapt work with const_array.

Author: vakokako

include/xtensor/xadapt.hpp

@@ -35,6 +35,12 @@ namespace xt
             static constexpr std::size_t value = N;
         };
 
+        template <class T, std::size_t N>
+        struct array_size_impl<const_array<T, N>>
+        {
+            static constexpr std::size_t value = N;
+        };
+
         template <class C>
         using array_size = array_size_impl<std::decay_t<C>>;
 

include/xtensor/xcontainer.hpp

@@ -52,6 +52,14 @@ namespace xt
         {
             using type = std::allocator<T>;  // fake allocator for testing
         };
+
+
+        template <class T, std::size_t N>
+        struct allocator_type_impl<const_array<T, N>>
+        {
+            using type = std::allocator<T>;  // fake allocator for testing
+        };
+
     }
 
     template <class T>

include/xtensor/xshape.hpp

@@ -351,6 +351,12 @@ namespace xt
         {
             static constexpr bool value = true;
         };
+        
+        template <class T, std::size_t N>
+        struct is_array<const_array<T, N>>
+        {
+            static constexpr bool value = true;
+        };
 
         template <class S>
         struct is_fixed : std::false_type