Merge pull request #679 from CaseyCarter/relax_view

Allow move-only single-pass Views
ericniebler · Jun 30, 2017 · cb42d1c · cb42d1c
2 parents c3ddc64 + 53bb133
commit cb42d1c
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Showing 45 changed files with 1,027 additions and 391 deletions.
diff --git a/include/range/v3/istream_range.hpp b/include/range/v3/istream_range.hpp
@@ -33,7 +33,7 @@ namespace ranges
         private:
             friend range_access;
             std::istream *sin_;
-            semiregular_t<Val> obj_;
+            movesemiregular_t<Val> obj_;
             struct cursor
             {
             private:

diff --git a/include/range/v3/range_concepts.hpp b/include/range/v3/range_concepts.hpp
@@ -204,12 +204,11 @@ namespace ranges
             ///
 
             struct View
-              : refines<Range>
+              : refines<Range, Movable, DefaultConstructible>
             {
                 template<typename T>
                 auto requires_() -> decltype(
                     concepts::valid_expr(
-                        concepts::model_of<SemiRegular, T>(),
                         concepts::is_true(detail::view_predicate_<T>())
                     ));
             };
@@ -223,7 +222,7 @@ namespace ranges
             {};
 
             struct ForwardView
-              : refines<InputView, ForwardRange>
+              : refines<InputView, ForwardRange, Copyable>
             {};
 
             struct BidirectionalView

diff --git a/include/range/v3/utility/memory.hpp b/include/range/v3/utility/memory.hpp
@@ -23,10 +23,11 @@
 
 #include <memory>
 #include <type_traits>
-#include <range/v3/range_fwd.hpp>
 #include <meta/meta.hpp>
+#include <range/v3/detail/config.hpp>
 #include <range/v3/utility/iterator_concepts.hpp>
 #include <range/v3/utility/iterator_traits.hpp>
+#include <range/v3/utility/polymorphic_cast.hpp>
 
 namespace ranges
 {
@@ -44,6 +45,13 @@ namespace ranges
                         std::return_temporary_buffer(p);
                 }
             };
+
+            template<typename T, typename... Args,
+                CONCEPT_REQUIRES_(!std::is_array<T>::value)>
+            std::unique_ptr<T> make_unique(Args &&... args)
+            {
+                return std::unique_ptr<T>{new T(static_cast<Args &&>(args)...)};
+            }
         }
         /// \endcond
 

diff --git a/include/range/v3/utility/polymorphic_cast.hpp b/include/range/v3/utility/polymorphic_cast.hpp
@@ -5,17 +5,37 @@
 
 #ifndef RANGES_V3_UTILITY_POLYMORPHIC_CAST_HPP
 #define RANGES_V3_UTILITY_POLYMORPHIC_CAST_HPP
+
+#include <memory>
+#include <type_traits>
+#include <meta/meta.hpp>
 #include <range/v3/detail/config.hpp>
 
 namespace ranges
 {
     inline namespace v3
     {
         template<typename Target, typename Source>
-        inline Target polymorphic_downcast(Source* x)
+        auto polymorphic_downcast(Source *x) noexcept ->
+            meta::if_<std::is_pointer<Target>,
+                decltype((static_cast<Target>(x), dynamic_cast<Target>(x)))>
+        {
+            auto result = static_cast<Target>(x);
+            RANGES_ASSERT(dynamic_cast<Target>(x) == result);
+            return result;
+        }
+        template<typename Target, typename Source>
+        auto polymorphic_downcast(Source &&x) noexcept ->
+            meta::if_<std::is_reference<Target>,
+                decltype((static_cast<Target>(std::declval<Source>()),
+                    dynamic_cast<Target>(std::declval<Source>())))>
         {
-            RANGES_ASSERT(dynamic_cast<Target>(x) == x);
-            return static_cast<Target>(x);
+            auto &&result = static_cast<Target>(static_cast<Source &&>(x));
+#ifndef NDEBUG
+            auto &&dresult = dynamic_cast<Target>(static_cast<Source &&>(x));
+            RANGES_ASSERT(std::addressof(dresult) == std::addressof(result));
+#endif
+            return static_cast<Target>(result);
         }
     }
 }

diff --git a/include/range/v3/utility/semiregular.hpp b/include/range/v3/utility/semiregular.hpp
@@ -195,6 +195,13 @@ namespace ranges
         using semiregular_t =
             meta::if_<SemiRegular<T>, T, semiregular<T>>;
 
+        template<typename T>
+        using movesemiregular_t =
+            meta::if_c<
+                Movable<T>() && DefaultConstructible<T>(),
+                T,
+                semiregular<T>>;
+
         template<typename T, bool IsConst = false>
         using semiregular_ref_or_val_t =
             meta::if_<