Closes #62

btas/util/sequence_adaptor.h

@@ -83,6 +83,33 @@ namespace std {
       // access
       operator type& () noexcept { return *this; }
       type& get() noexcept { return *this; }
+      const type& get() const noexcept { return *this; }
+
+  };
+
+  // re-implement reference_wrapper<const infinite_sequence_adaptor<Ptr>> to act like const Ptr
+  template <typename _T>
+  class reference_wrapper<const btas::infinite_sequence_adaptor<_T*>> : private btas::infinite_sequence_adaptor<_T*> {
+    public:
+
+      // types
+      typedef const btas::infinite_sequence_adaptor<_T*> ctype;
+      typedef btas::infinite_sequence_adaptor<_T*> nctype;
+
+      // construct/copy/destroy
+      reference_wrapper(ctype& x) noexcept : ctype(x) {}
+      // DO bind to temps
+      reference_wrapper(nctype&& x) noexcept : ctype(x) {}
+      reference_wrapper(const reference_wrapper<ctype>& x) noexcept : ctype(x) {}
+
+      // assignment
+      reference_wrapper& operator=(const reference_wrapper<ctype>& x) noexcept {
+        static_cast<ctype&>(*this) = static_cast<ctype&>(x);
+      }
+
+      // access
+      operator ctype& () const noexcept { return *this; }
+      ctype& get() const noexcept { return *this; }
 
   };
 

test/test.C

@@ -463,13 +463,14 @@ int main()
       auto map0   = make_map(ptr0, Range{2, 3, 4});   // writable map
       auto map0c  = make_map(const_cast<const double*>(ptr0), Range{2, 3, 4});   // const map
       auto map0c2 = make_cmap(ptr0, Range{2, 3, 4}); // const map
+      auto map0c3 = make_cmap(const_cast<const double*>(ptr0), Range{2, 3, 4});   // const map
 
       map0(1, 2, 3) = -1.0;
       //map0c(1, 2, 3) = -1.0;  // error: read-only map
       //map0c2(1, 2, 3) = -1.0; // error: read-only map
 
-      std::cout << map0 << std::endl;
-      for (const auto& i: map0) { std::cout << i << std::endl; }
+      std::cout << map0c << std::endl;
+      for (const auto& i: map0c) { std::cout << i << std::endl; }
 
       delete[] ptr0;
   }