Merge pull request #207 from tcbrindle/pr/default_sequence_traits

Add default_sequence_traits

include/flux/core/concepts.hpp

@@ -11,10 +11,18 @@
 #include <compare>
 #include <concepts>
 #include <cstdint>
+#include <functional>
 #include <initializer_list>
 #include <tuple>
 #include <type_traits>
 
+// clang-format off
+
+// Workaround GCC11/12 ICE in sequence concept definition below
+#if defined(__GNUC__) && !defined(__clang__) && (__GNUC__ < 13)
+#define FLUX_COMPILER_IS_GCC12
+#endif
+
 #if defined(__cpp_lib_ranges_zip) && (__cpp_lib_ranges_zip >= 202110L)
 #define FLUX_HAVE_CPP23_TUPLE_COMMON_REF
 #endif
@@ -46,6 +54,9 @@ FLUX_EXPORT
 template <typename T>
 struct sequence_traits;
 
+FLUX_EXPORT
+struct default_sequence_traits;
+
 namespace detail {
 
 template <typename T>
@@ -73,29 +84,6 @@ template <has_element_type T>
     requires requires { typename traits_t<T>::value_type; }
 struct value_type<T> { using type = typename traits_t<T>::value_type; };
 
-template <has_element_type T>
-    requires requires { traits_t<T>::using_primary_template; } &&
-             requires { typename T::value_type; }
-struct value_type<T> { using type = typename T::value_type; };
-
-template <has_element_type T>
-struct rvalue_element_type {
-    using type = std::conditional_t<std::is_lvalue_reference_v<element_t<T>>,
-                                    std::add_rvalue_reference_t<std::remove_reference_t<element_t<T>>>,
-                                    element_t<T>>;
-};
-
-template <typename Seq>
-concept has_move_at = requires (Seq& seq, cursor_t<Seq> const& cur) {
-   { traits_t<Seq>::move_at(seq, cur) };
-};
-
-template <has_element_type T>
-    requires has_move_at<T>
-struct rvalue_element_type<T> {
-    using type = decltype(traits_t<T>::move_at(FLUX_DECLVAL(T&), FLUX_DECLVAL(cursor_t<T> const&)));
-};
-
 } // namespace detail
 
 FLUX_EXPORT
@@ -110,7 +98,7 @@ using index_t = flux::config::int_type;
 
 FLUX_EXPORT
 template <typename Seq>
-using rvalue_element_t = typename detail::rvalue_element_type<Seq>::type;
+using rvalue_element_t = decltype(detail::traits_t<Seq>::move_at(FLUX_DECLVAL(Seq&), FLUX_DECLVAL(cursor_t<Seq> const&)));
 
 FLUX_EXPORT
 template <typename Seq>
@@ -136,7 +124,7 @@ template <typename T>
 concept can_reference = requires { typename with_ref<T>; };
 
 template <typename Seq, typename Traits = sequence_traits<std::remove_cvref_t<Seq>>>
-concept sequence_concept =
+concept sequence_requirements =
     requires (Seq& seq) {
         { Traits::first(seq) } -> cursor;
     } &&
@@ -146,7 +134,21 @@ concept sequence_concept =
     } &&
     requires (Seq& seq, cursor_t<Seq>& cur) {
         { Traits::inc(seq, cur) };
+    };
+
+template <typename Seq, typename Traits = sequence_traits<std::remove_cvref_t<Seq>>>
+concept sequence_concept =
+    sequence_requirements<Seq> &&
+    requires (Seq& seq, cursor_t<Seq> const& cur) {
+        { Traits::read_at_unchecked(seq, cur) } -> std::same_as<element_t<Seq>>;
+        { Traits::move_at(seq, cur) } -> can_reference;
+        { Traits::move_at_unchecked(seq, cur) } -> std::same_as<rvalue_element_t<Seq>>;
+    } &&
+#ifndef FLUX_COMPILER_IS_GCC12
+    requires (Seq& seq, bool (*pred)(element_t<Seq>)) {
+        { Traits::for_each_while(seq, pred) } -> std::same_as<cursor_t<Seq>>;
     } &&
+#endif
 #ifdef FLUX_HAVE_CPP23_TUPLE_COMMON_REF
     std::common_reference_with<element_t<Seq>&&, value_t<Seq>&> &&
     std::common_reference_with<rvalue_element_t<Seq>&&, value_t<Seq> const&> &&
@@ -180,8 +182,7 @@ concept multipass_sequence =
 namespace detail {
 
 template <typename Seq, typename Traits = sequence_traits<std::remove_cvref_t<Seq>>>
-concept bidirectional_sequence_concept =
-    multipass_sequence<Seq> &&
+concept bidirectional_sequence_requirements =
     requires (Seq& seq, cursor_t<Seq>& cur) {
         { Traits::dec(seq, cur) };
     };
@@ -190,13 +191,13 @@ concept bidirectional_sequence_concept =
 
 FLUX_EXPORT
 template <typename Seq>
-concept bidirectional_sequence = detail::bidirectional_sequence_concept<Seq>;
+concept bidirectional_sequence = multipass_sequence<Seq> && detail::bidirectional_sequence_requirements<Seq>;
 
 namespace detail {
 
 template <typename Seq, typename Traits = sequence_traits<std::remove_cvref_t<Seq>>>
-concept random_access_sequence_concept =
-    bidirectional_sequence<Seq> && ordered_cursor<cursor_t<Seq>> &&
+concept random_access_sequence_requirements =
+    ordered_cursor<cursor_t<Seq>> &&
     requires (Seq& seq, cursor_t<Seq>& cur, distance_t offset) {
         { Traits::inc(seq, cur, offset) };
     } &&
@@ -208,13 +209,14 @@ concept random_access_sequence_concept =
 
 FLUX_EXPORT
 template <typename Seq>
-concept random_access_sequence = detail::random_access_sequence_concept<Seq>;
+concept random_access_sequence =
+    bidirectional_sequence<Seq> &&
+    detail::random_access_sequence_requirements<Seq>;
 
 namespace detail {
 
 template <typename Seq, typename Traits = sequence_traits<std::remove_cvref_t<Seq>>>
-concept bounded_sequence_concept =
-    sequence<Seq> &&
+concept bounded_sequence_requirements =
     requires (Seq& seq) {
         { Traits::last(seq) } -> std::same_as<cursor_t<Seq>>;
     };
@@ -223,14 +225,12 @@ concept bounded_sequence_concept =
 
 FLUX_EXPORT
 template <typename Seq>
-concept bounded_sequence = detail::bounded_sequence_concept<Seq>;
+concept bounded_sequence = sequence<Seq> && detail::bounded_sequence_requirements<Seq>;
 
 namespace detail {
 
 template <typename Seq, typename Traits = sequence_traits<std::remove_cvref_t<Seq>>>
-concept contiguous_sequence_concept =
-    random_access_sequence<Seq> &&
-    bounded_sequence<Seq> &&
+concept contiguous_sequence_requirements =
     std::is_lvalue_reference_v<element_t<Seq>> &&
     std::same_as<value_t<Seq>, std::remove_cvref_t<element_t<Seq>>> &&
     requires (Seq& seq) {
@@ -241,24 +241,24 @@ concept contiguous_sequence_concept =
 
 FLUX_EXPORT
 template <typename Seq>
-concept contiguous_sequence = detail::contiguous_sequence_concept<Seq>;
+concept contiguous_sequence =
+    random_access_sequence<Seq> &&
+    bounded_sequence<Seq> &&
+    detail::contiguous_sequence_requirements<Seq>;
 
 namespace detail {
 
 template <typename Seq, typename Traits = sequence_traits<std::remove_cvref_t<Seq>>>
-concept sized_sequence_concept =
-    sequence<Seq> &&
-    (requires (Seq& seq) {
+concept sized_sequence_requirements =
+    requires (Seq& seq) {
         { Traits::size(seq) } -> std::convertible_to<distance_t>;
-    } || (
-        random_access_sequence<Seq> && bounded_sequence<Seq>
-    ));
+    };
 
 } // namespace detail
 
 FLUX_EXPORT
 template <typename Seq>
-concept sized_sequence = detail::sized_sequence_concept<Seq>;
+concept sized_sequence = sequence<Seq> && detail::sized_sequence_requirements<Seq>;
 
 FLUX_EXPORT
 template <typename Seq, typename T>
@@ -366,6 +366,77 @@ concept derived_from_inline_sequence_base = requires(T t) {
 /*
  * Default sequence_traits implementation
  */
+
+struct default_sequence_traits {
+
+    template <typename Self>
+        requires detail::sequence_requirements<Self>
+    static constexpr auto read_at_unchecked(Self& self, cursor_t<Self> const& cur)
+        -> decltype(detail::traits_t<Self>::read_at(self, cur))
+    {
+        return detail::traits_t<Self>::read_at(self, cur);
+    }
+
+    template <typename Self>
+        requires detail::sequence_requirements<Self>
+    static constexpr auto move_at(Self& self, cursor_t<Self> const& cur)
+        -> std::conditional_t<std::is_lvalue_reference_v<element_t<Self>>,
+                              std::add_rvalue_reference_t<std::remove_reference_t<element_t<Self>>>,
+                              element_t<Self>>
+    {
+        using Traits = detail::traits_t<Self>;
+        if constexpr (std::is_lvalue_reference_v<element_t<Self>>) {
+            return std::move(Traits::read_at(self, cur));
+        } else {
+            return Traits::read_at(self, cur);
+        }
+    }
+
+    template <typename Self>
+        requires detail::sequence_requirements<Self>
+    static constexpr auto move_at_unchecked(Self& self, cursor_t<Self> const& cur)
+        -> decltype(detail::traits_t<Self>::move_at(self, cur))
+    {
+        return detail::traits_t<Self>::move_at(self, cur);
+    }
+
+    template <typename Self>
+        requires detail::random_access_sequence_requirements<Self> &&
+                 detail::bounded_sequence_requirements<Self>
+    static constexpr auto size(Self& self) -> distance_t
+    {
+        using Traits = detail::traits_t<Self>;
+        return Traits::distance(self, Traits::first(self), Traits::last(self));
+    }
+
+    template <typename Self, typename Pred>
+        requires detail::sequence_requirements<Self>
+    static constexpr auto for_each_while(Self& self, Pred&& pred) -> cursor_t<Self>
+    {
+        using Traits = detail::traits_t<Self>;
+
+        auto cur = Traits::first(self);
+        if constexpr (bounded_sequence<Self> && regular_cursor<cursor_t<Self>>) {
+            auto const last = Traits::last(self);
+            while (cur != last) {
+                if (!std::invoke(pred, Traits::read_at(self, cur))) {
+                    break;
+                }
+                Traits::inc(self, cur);
+            }
+        } else {
+            while (!Traits::is_last(self, cur)) {
+                if (!std::invoke(pred, Traits::read_at(self, cur))) {
+                    break;
+                }
+                Traits::inc(self, cur);
+            }
+        }
+        return cur;
+    }
+
+};
+
 namespace detail {
 
 template <typename T>

include/flux/core/default_impls.hpp

@@ -18,7 +18,7 @@ namespace flux {
  * Default implementation for C arrays of known bound
  */
 template <typename T, index_t N>
-struct sequence_traits<T[N]> {
+struct sequence_traits<T[N]> : default_sequence_traits {
 
     static constexpr auto first(auto const&) -> index_t { return index_t{0}; }
 
@@ -82,7 +82,7 @@ struct sequence_traits<T[N]> {
  * Default implementation for std::reference_wrapper<T>
  */
 template <sequence Seq>
-struct sequence_traits<std::reference_wrapper<Seq>> {
+struct sequence_traits<std::reference_wrapper<Seq>> : default_sequence_traits {
 
     using self_t = std::reference_wrapper<Seq>;
 
@@ -172,7 +172,7 @@ template <typename R>
              std::ranges::sized_range<R> &&
              std::ranges::contiguous_range<R const> &&
              std::ranges::sized_range<R const>)
-struct sequence_traits<R> {
+struct sequence_traits<R> : default_sequence_traits {
 
     using value_type = std::ranges::range_value_t<R>;
 

include/flux/core/sequence_access.hpp

@@ -117,12 +117,7 @@ struct size_fn {
     [[nodiscard]]
     constexpr auto operator()(Seq&& seq) const -> distance_t
     {
-        if constexpr (requires { traits_t<Seq>::size(seq); }) {
-            return traits_t<Seq>::size(seq);
-        } else {
-            static_assert(bounded_sequence<Seq> && random_access_sequence<Seq>);
-            return distance_fn{}(seq, first_fn{}(seq), last_fn{}(seq));
-        }
+        return traits_t<Seq>::size(seq);
     }
 };
 
@@ -135,74 +130,33 @@ struct usize_fn {
     }
 };
 
-template <typename Seq>
-concept has_custom_move_at =
-    sequence<Seq> &&
-    requires (Seq& seq, cursor_t<Seq> const& cur) {
-        { traits_t<Seq>::move_at(seq, cur) };
-    };
-
 struct move_at_fn {
     template <sequence Seq>
     [[nodiscard]]
     constexpr auto operator()(Seq& seq, cursor_t<Seq> const& cur) const
         -> rvalue_element_t<Seq>
     {
-        if constexpr (has_custom_move_at<Seq>) {
-            return traits_t<Seq>::move_at(seq, cur);
-        } else {
-            if constexpr (std::is_lvalue_reference_v<element_t<Seq>>) {
-                return std::move(read_at_fn{}(seq, cur));
-            } else {
-                return read_at_fn{}(seq, cur);
-            }
-        }
+        return traits_t<Seq>::move_at(seq, cur);
     }
 };
 
-template <typename Seq>
-concept has_custom_read_at_unchecked =
-    sequence<Seq> &&
-    requires (Seq& seq, cursor_t<Seq> const& cur) {
-        { traits_t<Seq>::read_at_unchecked(seq, cur) } -> std::same_as<element_t<Seq>>;
-    };
-
 struct read_at_unchecked_fn {
     template <sequence Seq>
     [[nodiscard]]
     constexpr auto operator()(Seq& seq, cursor_t<Seq> const& cur) const
         -> element_t<Seq>
     {
-        if constexpr (has_custom_read_at_unchecked<Seq>) {
-            return traits_t<Seq>::read_at_unchecked(seq, cur);
-        } else {
-            return read_at_fn{}(seq, cur);
-        }
+        return traits_t<Seq>::read_at_unchecked(seq, cur);
     }
 };
 
-template <typename Seq>
-concept has_custom_move_at_unchecked =
-    sequence<Seq> &&
-    requires (Seq& seq, cursor_t<Seq> const& cur) {
-        { traits_t<Seq>::move_at_unchecked(seq, cur) } -> std::same_as<rvalue_element_t<Seq>>;
-};
-
 struct move_at_unchecked_fn {
     template <sequence Seq>
     [[nodiscard]]
     constexpr auto operator()(Seq& seq, cursor_t<Seq> const& cur) const
         -> rvalue_element_t<Seq>
     {
-        if constexpr (has_custom_move_at_unchecked<Seq>) {
-            return traits_t<Seq>::move_at_unchecked(seq, cur);
-        } else if constexpr (has_custom_move_at<Seq>) {
-            return move_at_fn{}(seq, cur);
-        } else if constexpr (std::is_lvalue_reference_v<element_t<Seq>>){
-            return std::move(read_at_unchecked_fn{}(seq, cur));
-        } else {
-            return read_at_unchecked_fn{}(seq, cur);
-        }
+        return traits_t<Seq>::move_at_unchecked(seq, cur);
     }
 };
 

include/flux/op/adjacent.hpp

@@ -22,7 +22,7 @@ namespace flux {
 namespace detail {
 
 template <typename Base, distance_t N>
-struct adjacent_sequence_traits_base {
+struct adjacent_sequence_traits_base : default_sequence_traits {
 protected:
     struct cursor_type {
         std::array<cursor_t<Base>, N> arr{};