Fix (#10)

include/preview/__iterator/basic_const_iterator.h

@@ -15,6 +15,7 @@
 #include "preview/__concepts/same_as.h"
 #include "preview/__concepts/semiregular.h"
 #include "preview/__concepts/totally_ordered.h"
+#include "preview/__iterator/detail/have_cxx20_iterator.h"
 #include "preview/__iterator/bidirectional_iterator.h"
 #include "preview/__iterator/contiguous_iterator.h"
 #include "preview/__iterator/forward_iterator.h"
@@ -30,6 +31,7 @@
 #include "preview/__memory/addressof.h"
 #include "preview/__memory/to_address.h"
 #include "preview/__type_traits/common_reference.h"
+#include "preview/__type_traits/conditional.h"
 #include "preview/__type_traits/conjunction.h"
 #include "preview/__type_traits/is_specialization.h"
 #include "preview/__type_traits/is_nothrow_convertible.h"
@@ -48,24 +50,21 @@ struct basic_const_iterator_category {
 
 template<typename Iter>
 struct basic_const_iterator_category<Iter, false> {
-#if __cplusplus < 202002L
+#if !PREVIEW_STD_HAVE_CXX20_ITERATOR
   using iterator_category = iterator_ignore;
 #endif
 };
 
 template<typename Iter>
 struct basic_const_iterator_concept {
   using iterator_concept =
-    std::conditional_t<
-      contiguous_iterator<Iter>::value, contiguous_iterator_tag,
-    std::conditional_t<
-      random_access_iterator<Iter>::value, random_access_iterator_tag,
-    std::conditional_t<
-      bidirectional_iterator<Iter>::value, bidirectional_iterator_tag,
-    std::conditional_t<
-      forward_iterator<Iter>::value, forward_iterator_tag,
+    conditional_t<
+      contiguous_iterator<Iter>, contiguous_iterator_tag,
+      random_access_iterator<Iter>, random_access_iterator_tag,
+      bidirectional_iterator<Iter>, bidirectional_iterator_tag,
+      forward_iterator<Iter>, forward_iterator_tag,
       input_iterator_tag
-    >>>>;
+    >;
 };
 
 template<typename I, bool = input_iterator<I>::value /* false */>

include/preview/__iterator/common_iterator.h

@@ -18,6 +18,7 @@
 #include "preview/__concepts/equality_comparable.h"
 #include "preview/__concepts/move_constructible.h"
 #include "preview/__concepts/same_as.h"
+#include "preview/__iterator/detail/have_cxx20_iterator.h"
 #include "preview/__iterator/forward_iterator.h"
 #include "preview/__iterator/incrementable_traits.h"
 #include "preview/__iterator/indirectly_readable.h"
@@ -350,7 +351,7 @@ namespace detail {
 
 template<typename I, bool = std::is_integral<iter_difference_t<I>>::value /* false */>
 struct common_iterator_category {
-#if __cplusplus < 202002L
+#if !PREVIEW_STD_HAVE_CXX20_ITERATOR
   using iterator_category = iterator_ignore;
 #endif
 };

include/preview/__iterator/counted_iterator.h

@@ -14,7 +14,7 @@
 #include "preview/__concepts/common_with.h"
 #include "preview/__concepts/convertible_to.h"
 #include "preview/__concepts/dereferenceable.h"
-#include "preview/__iterator/detail/std_check.h"
+#include "preview/__iterator/detail/have_cxx20_iterator.h"
 #include "preview/__iterator/contiguous_iterator.h"
 #include "preview/__iterator/iterator_traits.h"
 #include "preview/__iterator/bidirectional_iterator.h"

include/preview/__iterator/detail/have_cxx20_iterator.h

@@ -0,0 +1,34 @@
+# /**
+#  * Created by YongGyu Lee on 2024. 6. 16..
+#  */
+#
+# ifndef PREVIEW_ITERATOR_DETAIL_STD_CHECK_H_
+# define PREVIEW_ITERATOR_DETAIL_STD_CHECK_H_
+#
+# include <iterator>
+#
+# include "preview/core.h"
+#
+# /* TODO: Not use this when defining views::iterator */
+# if PREVIEW_CXX_VERSION >= 20 && (PREVIEW_ANDROID == 0 || (defined(PREVIEW_NDK_VERSION_MAJOR) && PREVIEW_NDK_VERSION_MAJOR >= 26))
+#   define PREVIEW_STD_HAVE_CXX20_ITERATOR 1
+# else
+#   define PREVIEW_STD_HAVE_CXX20_ITERATOR 0
+# endif
+
+// TODO: Test using template
+//namespace preview {
+//namespace detail {
+//
+//template<typename T>
+//struct cxx20_iterator_tester {
+//  using difference_type = int;
+//  using value_type = int;
+//  using reference = int&;
+//  using iterator_category = std::input_iterator_tag;
+//};
+//
+//} // namespace preview
+//} // namespace preview
+
+# endif // PREVIEW_ITERATOR_DETAIL_STD_CHECK_H_

include/preview/__iterator/indirectly_readable_traits.h

@@ -23,8 +23,8 @@ struct value_typer {
 
 template<
     typename T,
-    bool = has_typename_value_type<T>::value,
-    bool = has_typename_element_type<T>::value
+    bool = has_typename_value_type<T>::value, /* false */
+    bool = has_typename_element_type<T>::value /* false */
 >
 struct indirectly_readable_traits_impl {};
 

include/preview/__iterator/std_common_iterator.h

@@ -5,7 +5,7 @@
 #ifndef PREVIEW_ITERATOR_STD_COMMON_ITERATOR_H_
 #define PREVIEW_ITERATOR_STD_COMMON_ITERATOR_H_
 
-#include "preview/__iterator/detail/std_check.h"
+#include "preview/__iterator/detail/have_cxx20_iterator.h"
 
 #if PREVIEW_STD_HAVE_CXX20_ITERATOR
 

include/preview/__iterator/std_counted_iterator.h

@@ -5,7 +5,7 @@
 #ifndef PREVIEW_ITERATOR_STD_COUNTED_ITERATOR_H_
 #define PREVIEW_ITERATOR_STD_COUNTED_ITERATOR_H_
 
-#include "preview/__iterator/detail/std_check.h"
+#include "preview/__iterator/detail/have_cxx20_iterator.h"
 
 #if PREVIEW_STD_HAVE_CXX20_ITERATOR
 

include/preview/__ranges/views/basic_istream_view.h

@@ -12,6 +12,7 @@
 
 #include "preview/__concepts/default_initializable.h"
 #include "preview/__concepts/movable.h"
+#include "preview/__iterator/detail/have_cxx20_iterator.h"
 #include "preview/__iterator/default_sentinel_t.h"
 #include "preview/__iterator/iterator_tag.h"
 #include "preview/__memory/addressof.h"
@@ -43,7 +44,7 @@ class basic_istream_view : public view_interface<basic_istream_view<Val, CharT,
     using iterator_concept = input_iterator_tag;
     using difference_type = std::ptrdiff_t;
     using value_type = Val;
-#if __cplusplus < 202002L
+#if !PREVIEW_STD_HAVE_CXX20_ITERATOR
     using iterator_category = iterator_ignore;
     using pointer = void;
     using reference = Val&;

include/preview/__ranges/views/cartesian_product_view.h

@@ -12,6 +12,7 @@
 
 #include "preview/__concepts/equality_comparable.h"
 #include "preview/__iterator/default_sentinel_t.h"
+#include "preview/__iterator/detail/have_cxx20_iterator.h"
 #include "preview/__iterator/indirectly_swappable.h"
 #include "preview/__iterator/iterator_tag.h"
 #include "preview/__iterator/iter_move.h"
@@ -34,6 +35,7 @@
 #include "preview/__ranges/view_interface.h"
 #include "preview/__tuple/tuple_transform.h"
 #include "preview/__type_traits/bool_constant.h"
+#include "preview/__type_traits/conditional.h"
 #include "preview/__type_traits/conjunction.h"
 #include "preview/__type_traits/disjunction.h"
 #include "preview/__type_traits/maybe_const.h"
@@ -188,22 +190,20 @@ class cartesian_product_view : public view_interface<cartesian_product_view<Firs
    public:
     using iterator_category = input_iterator_tag;
     using iterator_concept =
-        std::conditional_t<
-            detail::cartesian_product_is_random_access<Const, First, Vs...>::value, random_access_iterator_tag,
-        std::conditional_t<
-            detail::cartesian_product_is_bidirectional<Const, First, Vs...>::value, bidirectional_iterator_tag,
-        std::conditional_t<
-            forward_range<maybe_const<Const, First>>::value, forward_iterator_tag,
+        conditional_t<
+            detail::cartesian_product_is_random_access<Const, First, Vs...>, random_access_iterator_tag,
+            detail::cartesian_product_is_bidirectional<Const, First, Vs...>, bidirectional_iterator_tag,
+            forward_range<maybe_const<Const, First>>, forward_iterator_tag,
             input_iterator_tag
-        >>>;
+        >;
     using value_type = std::tuple<
         range_value_t<maybe_const<Const, First>>,
         range_value_t<maybe_const<Const, Vs   >>... >;
     using reference = std::tuple<
         range_reference_t<maybe_const<Const, First>>,
         range_reference_t<maybe_const<Const, Vs   >>... >;
     using difference_type = int;
-#if __cplusplus < 202002L
+#if !PREVIEW_STD_HAVE_CXX20_ITERATOR
     using pointer = void;
 #endif
 

include/preview/__ranges/views/concat_view.h

@@ -21,6 +21,7 @@
 #include "preview/__ranges/views/all.h"
 #include "preview/__tuple/tuple_fold.h"
 #include "preview/__tuple/tuple_transform.h"
+#include "preview/__type_traits/conditional.h"
 #include "preview/__type_traits/conjunction.h"
 #include "preview/__type_traits/common_type.h"
 #include "preview/__type_traits/common_reference.h"
@@ -89,14 +90,12 @@ struct concat_view : view_interface<concat_view<Rngs...>> {
   struct iterator {
     using iterator_category = input_iterator_tag;
     using iterator_concept =
-        std::conditional_t<
-            conjunction<random_access_range<Rngs>...>::value, random_access_iterator_tag,
-        std::conditional_t<
-            conjunction<bidirectional_range<Rngs>...>::value, bidirectional_iterator_tag,
-        std::conditional_t<
-            conjunction<forward_range<Rngs>...>::value, forward_iterator_tag,
+        conditional_t<
+            conjunction<random_access_range<Rngs>...>, random_access_iterator_tag,
+            conjunction<bidirectional_range<Rngs>...>, bidirectional_iterator_tag,
+            conjunction<forward_range<Rngs>...>, forward_iterator_tag,
             input_iterator_tag
-        >>>;
+        >;
     using value_type = common_type_t<range_value_t<maybe_const<IsConst, Rngs>>...>;
     using difference_type = common_type_t<range_difference_t<Rngs>...>;
     using reference = common_reference_t<range_reference_t<maybe_const<IsConst, Rngs>>...>;

include/preview/__ranges/views/elements_view.h

@@ -14,6 +14,7 @@
 #include "preview/__concepts/convertible_to.h"
 #include "preview/__concepts/derived_from.h"
 #include "preview/__concepts/move_constructible.h"
+#include "preview/__iterator/detail/have_cxx20_iterator.h"
 #include "preview/__iterator/iterator_tag.h"
 #include "preview/__iterator/iterator_traits.h"
 #include "preview/__ranges/begin.h"
@@ -33,6 +34,7 @@
 #include "preview/__ranges/viewable_range.h"
 #include "preview/__tuple/tuple_like.h"
 #include "preview/__type_traits/bool_constant.h"
+#include "preview/__type_traits/conditional.h"
 #include "preview/__type_traits/conjunction.h"
 #include "preview/__type_traits/disjunction.h"
 #include "preview/__type_traits/has_typename_type.h"
@@ -64,7 +66,7 @@ struct returnable_element<T, N, false, true>
 // Not defined, if Base does not model forward_range
 template<typename Base, std::size_t N, bool = forward_range<Base>::value /* false */>
 struct elements_view_iterator_category {
-#if __cplusplus < 202002L
+#if !PREVIEW_STD_HAVE_CXX20_ITERATOR
   using iterator_category = iterator_ignore;
 #endif
 };
@@ -76,12 +78,11 @@ struct elements_view_iterator_category<Base, N, true> {
 
  public:
   using iterator_category =
-      std::conditional_t<
-          std::is_rvalue_reference<decltype(std::get<N>(*std::declval<iterator_t<Base>&>()))>::value, input_iterator_tag,
-      std::conditional_t<
-          derived_from<C, random_access_iterator_tag>::value, random_access_iterator_tag,
+      conditional_t<
+          std::is_rvalue_reference<decltype(std::get<N>(*std::declval<iterator_t<Base>&>()))>, input_iterator_tag,
+          derived_from<C, random_access_iterator_tag>, random_access_iterator_tag,
           C
-      >>;
+      >;
 };
 
 } // namespace detail
@@ -114,17 +115,15 @@ class elements_view : public view_interface<elements_view<V, N>> {
 
    public:
     using iterator_concept =
-        std::conditional_t<
-            random_access_range<Base>::value, random_access_iterator_tag,
-        std::conditional_t<
-            bidirectional_range<Base>::value, bidirectional_iterator_tag,
-        std::conditional_t<
-            forward_range<Base>::value, forward_iterator_tag,
+        conditional_t<
+            random_access_range<Base>, random_access_iterator_tag,
+            bidirectional_range<Base>, bidirectional_iterator_tag,
+            forward_range<Base>, forward_iterator_tag,
             input_iterator_tag
-        >>>;
+        >;
     using value_type = remove_cvref_t<std::tuple_element_t<N, range_value_t<Base>>>;
     using difference_type = range_difference_t<Base>;
-#if __cplusplus < 202002L
+#if !PREVIEW_STD_HAVE_CXX20_ITERATOR
     using pointer = void;
     using reference = typename iterator_reference<range_reference_t<Base>>::type;
 #endif

include/preview/__ranges/views/enumerate_view.h

@@ -38,6 +38,7 @@
 #include "preview/__ranges/views/all.h"
 #endif
 #include "preview/__type_traits/bool_constant.h"
+#include "preview/__type_traits/conditional.h"
 #include "preview/__type_traits/conjunction.h"
 #include "preview/__type_traits/maybe_const.h"
 #include "preview/__utility/cxx20_rel_ops.h"
@@ -77,14 +78,12 @@ class enumerate_view : public view_interface<enumerate_view<V>> {
    public:
     using iterator_category = input_iterator_tag;
     using iterator_concept =
-        std::conditional_t<
-            random_access_range<Base>::value, random_access_iterator_tag,
-        std::conditional_t<
-            bidirectional_range<Base>::value, bidirectional_iterator_tag,
-        std::conditional_t<
-            forward_range<Base>::value, forward_iterator_tag,
+        conditional_t<
+            random_access_range<Base>, random_access_iterator_tag,
+            bidirectional_range<Base>, bidirectional_iterator_tag,
+            forward_range<Base>, forward_iterator_tag,
             input_iterator_tag
-        >>>;
+        >;
     using difference_type = range_difference_t<Base>;
     using value_type = Tuple<difference_type, range_value_t<Base>>;
     using pointer = void;