libstdc++: Simplify ranges::to closure objects

We can use the existing _Partial range adaptor closure object for
ranges::to instead of essentially reimplementing it.

libstdc++-v3/ChangeLog:

	* include/std/ranges (__detail::_ToClosure): Replace with ...
	(__detail::_To): ... this.
	(__detail::_ToClosure2): Replace with ...
	(__detail::To2): ... this.
	(to): Simplify using the existing _Partial range adaptor
	closure object.

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index afd0a38e0cfe0a40b874a54f944102f13d1efb0f..fb9df3d3e79bdf860db148e1fde9cadc91555da8 100644 (file)
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -1007,6 +1007,7 @@ namespace views::__adaptor
 
       // Invoke _Adaptor with arguments __r, _M_args... according to the
       // value category of this _Partial object.
+      // TODO: use explicit object functions ("deducing this").
       template<typename _Range>
        requires __adaptor_invocable<_Adaptor, _Range, const _Args&...>
        constexpr auto
@@ -1137,6 +1138,7 @@ namespace views::__adaptor
 
       // Invoke _M_rhs(_M_lhs(__r)) according to the value category of this
       // range adaptor closure object.
+      // TODO: use explicit object functions ("deducing this").
       template<typename _Range>
        requires __pipe_invocable<const _Lhs&, const _Rhs&, _Range>
        constexpr auto
@@ -9387,58 +9389,15 @@ namespace __detail
 /// @cond undocumented
 namespace __detail
 {
-  template<typename _Cont, typename... _Args>
-    class _ToClosure
-    : public views::__adaptor::_RangeAdaptorClosure<_ToClosure<_Cont, _Args...>>
+  template<typename _Cont>
+    struct _To
     {
-      tuple<decay_t<_Args>...> _M_bound_args;
-
-    public:
-      constexpr
-      _ToClosure(_Args&&... __args)
-      : _M_bound_args(std::forward<_Args>(__args)...)
-      { }
-
-      // TODO: use explicit object functions ("deducing this").
-
-      template<typename _Rg>
-       constexpr auto
-       operator()(_Rg&& __r) &
-       {
-         return std::apply([&__r]<typename... _Tp>(_Tp&&... __args) {
-           return ranges::to<_Cont>(std::forward<_Rg>(__r),
-                                    std::forward<_Tp>(__args)...);
-         }, _M_bound_args);
-       }
-
-      template<typename _Rg>
-       constexpr auto
-       operator()(_Rg&& __r) const &
-       {
-         return std::apply([&__r]<typename... _Tp>(_Tp&&... __args) {
-           return ranges::to<_Cont>(std::forward<_Rg>(__r),
-                                    std::forward<_Tp>(__args)...);
-         }, _M_bound_args);
-       }
-
-      template<typename _Rg>
+      template<typename _Range, typename... _Args>
        constexpr auto
-       operator()(_Rg&& __r) &&
+       operator()(_Range&& __r, _Args&&... __args) const
        {
-         return std::apply([&__r]<typename... _Tp>(_Tp&&... __args) {
-           return ranges::to<_Cont>(std::forward<_Rg>(__r),
-                                    std::forward<_Tp>(__args)...);
-         }, std::move(_M_bound_args));
-       }
-
-      template<typename _Rg>
-       constexpr auto
-       operator()(_Rg&& __r) const &&
-       {
-         return std::apply([&__r]<typename... _Tp>(_Tp&&... __args) {
-           return ranges::to<_Cont>(std::forward<_Rg>(__r),
-                                    std::forward<_Tp>(__args)...);
-         }, std::move(_M_bound_args));
+         return ranges::to<_Cont>(std::forward<_Range>(__r),
+                                  std::forward<_Args>(__args)...);
        }
     };
 } // namespace __detail
@@ -9461,65 +9420,26 @@ namespace __detail
    */
   template<typename _Cont, typename... _Args>
     requires (!view<_Cont>)
-    constexpr __detail::_ToClosure<_Cont, _Args...>
+    constexpr auto
     to [[nodiscard]] (_Args&&... __args)
-    { return {std::forward<_Args>(__args)...}; }
+    {
+      using __detail::_To;
+      using views::__adaptor::_Partial;
+      return _Partial<_To<_Cont>, decay_t<_Args>...>{std::forward<_Args>(__args)...};
+    }
 
 /// @cond undocumented
 namespace __detail
 {
-  template<template<typename...> typename _Cont, typename... _Args>
-    class _ToClosure2
-    : public views::__adaptor::_RangeAdaptorClosure<_ToClosure2<_Cont, _Args...>>
+  template<template<typename...> typename _Cont>
+    struct _To2
     {
-      tuple<decay_t<_Args>...> _M_bound_args;
-
-    public:
-      constexpr
-      _ToClosure2(_Args&&... __args)
-      : _M_bound_args(std::forward<_Args>(__args)...)
-      { }
-
-      // TODO: use explicit object functions ("deducing this").
-
-      template<typename _Rg>
-       constexpr auto
-       operator()(_Rg&& __r) &
-       {
-         return std::apply([&__r]<typename... _Tp>(_Tp&&... __args) {
-           return ranges::to<_Cont>(std::forward<_Rg>(__r),
-                                    std::forward<_Tp>(__args)...);
-         }, _M_bound_args);
-       }
-
-      template<typename _Rg>
-       constexpr auto
-       operator()(_Rg&& __r) const &
-       {
-         return std::apply([&__r]<typename... _Tp>(_Tp&&... __args) {
-           return ranges::to<_Cont>(std::forward<_Rg>(__r),
-                                    std::forward<_Tp>(__args)...);
-         }, _M_bound_args);
-       }
-
-      template<typename _Rg>
-       constexpr auto
-       operator()(_Rg&& __r) &&
-       {
-         return std::apply([&__r]<typename... _Tp>(_Tp&&... __args) {
-           return ranges::to<_Cont>(std::forward<_Rg>(__r),
-                                    std::forward<_Tp>(__args)...);
-         }, std::move(_M_bound_args));
-       }
-
-      template<typename _Rg>
+      template<typename _Range, typename... _Args>
        constexpr auto
-       operator()(_Rg&& __r) const &&
+       operator()(_Range&& __r, _Args&&... __args) const
        {
-         return std::apply([&__r]<typename... _Tp>(_Tp&&... __args) {
-           return ranges::to<_Cont>(std::forward<_Rg>(__r),
-                                    std::forward<_Tp>(__args)...);
-         }, std::move(_M_bound_args));
+         return ranges::to<_Cont>(std::forward<_Range>(__r),
+                                  std::forward<_Args>(__args)...);
        }
     };
 } // namespace __detail
@@ -9543,9 +9463,13 @@ namespace __detail
    * `r | std::ranges::to<std::vector>(an_allocator)`.
    */
   template<template<typename...> typename _Cont, typename... _Args>
-    constexpr __detail::_ToClosure2<_Cont, _Args...>
+    constexpr auto
     to [[nodiscard]] (_Args&&... __args)
-    { return {std::forward<_Args>(__args)...}; }
+    {
+      using __detail::_To2;
+      using views::__adaptor::_Partial;
+      return _Partial<_To2<_Cont>, decay_t<_Args>...>{std::forward<_Args>(__args)...};
+    }
 
 } // namespace ranges
 #endif // __cpp_lib_ranges_to_container