msvetkin/feat/export-helpers

docs/design_rationale.md

@@ -218,12 +218,11 @@ zero changes to the library or to the box types.
 template <beman::monadics::box Box>
     requires beman::monadics::box<typename beman::monadics::get_box_traits<Box>::value_type>
 constexpr auto flatten(Box&& box) {
-    using Traits    = beman::monadics::get_box_traits<Box>;
-    using InnerBox  = typename Traits::value_type;
-    using ITraits   = beman::monadics::get_box_traits<InnerBox>;
+    using Traits   = beman::monadics::get_box_traits<Box>;
+    using InnerBox = typename Traits::value_type;
 
     if (!Traits::has_value(box))
-        return ITraits::make_error(Traits::error(std::forward<Box>(box)));
+        return beman::monadics::propagate_error<InnerBox>(std::forward<Box>(box));
     return Traits::value(std::forward<Box>(box));
 }
 ```

include/beman/monadics/CMakeLists.txt

@@ -28,8 +28,8 @@ target_sources(
                 detail/meta_rebind.hpp
                 detail/or_else.hpp
                 detail/pipe_adaptor.hpp
-                detail/rebox_value.hpp
-                detail/rebox_error.hpp
+                detail/propagate_value.hpp
+                detail/propagate_error.hpp
                 detail/same_box.hpp
                 detail/same_unqualified_as.hpp
                 detail/transform.hpp

include/beman/monadics/detail/and_then.hpp

@@ -6,7 +6,7 @@
 #include <beman/monadics/detail/get_box_traits.hpp>
 #include <beman/monadics/detail/invoke_with_value.hpp>
 #include <beman/monadics/detail/pipe_adaptor.hpp>
-#include <beman/monadics/detail/rebox_error.hpp>
+#include <beman/monadics/detail/propagate_error.hpp>
 #include <beman/monadics/detail/same_box.hpp>
 
 #include <utility>
@@ -37,7 +37,7 @@ class and_then_t {
 
         using NewBox = decltype(invoke_with_value(std::forward<Op>(op).callable(key), std::forward<Box>(box)));
 
-        return rebox_error<NewBox>(std::forward<Box>(box));
+        return propagate_error<NewBox>(std::forward<Box>(box));
     }
 };
 

include/beman/monadics/detail/invoke_with_error.hpp

@@ -11,13 +11,20 @@
 namespace beman::monadics::detail {
 
 template<typename Fn, typename Box, typename Traits = get_box_traits<Box>>
-[[nodiscard]] constexpr decltype(auto) invoke_with_error(Fn&& fn, Box&& box) noexcept
-    requires requires {
-        { Traits::error(std::forward<Box>(box)) };
-        { std::forward<Fn>(fn)(Traits::error(std::forward<Box>(box))) };
-    } || requires { requires std::invocable<Fn>; }
+concept invocable_with_error = requires {
+    requires has_error_channel<Box>;
+    { std::declval<Fn>()(Traits::error(std::declval<Box>())) };
+} || requires {
+    requires !has_error_channel<Box>;
+    requires std::invocable<Fn>;
+};
+
+template<typename Fn, box Box>
+[[nodiscard]] constexpr decltype(auto) invoke_with_error(Fn&& fn, Box&& box)
+    requires invocable_with_error<decltype(fn), decltype(box)>
 {
-    if constexpr (requires { Traits::error(std::forward<Box>(box)); }) {
+    using Traits = get_box_traits<Box>;
+    if constexpr (has_error_channel<Box>) {
         return std::forward<Fn>(fn)(Traits::error(std::forward<Box>(box)));
     } else {
         return std::forward<Fn>(fn)();

include/beman/monadics/detail/invoke_with_value.hpp

@@ -10,15 +10,19 @@
 
 namespace beman::monadics::detail {
 
-template<typename Fn, box Box, typename Traits = get_box_traits<Box>>
-[[nodiscard]] constexpr decltype(auto) invoke_with_value(Fn&& fn, Box&& box) noexcept
-    requires requires {
-        { Traits::value(std::forward<Box>(box)) } -> std::same_as<void>;
-        { fn() };
-    } || requires {
-        { fn(Traits::value(std::forward<Box>(box))) };
-    }
+template<typename Fn, typename Box, typename Traits = get_box_traits<Box>>
+concept invocable_with_value = requires {
+    requires std::is_void_v<typename Traits::value_type>;
+    requires std::invocable<Fn>;
+} || requires {
+    { std::declval<Fn>()(Traits::value(std::declval<Box>())) };
+};
+
+template<typename Fn, box Box>
+[[nodiscard]] constexpr decltype(auto) invoke_with_value(Fn&& fn, Box&& box)
+    requires invocable_with_value<decltype(fn), decltype(box)>
 {
+    using Traits = get_box_traits<Box>;
     if constexpr (std::is_void_v<typename Traits::value_type> && std::invocable<Fn>) {
         // should just invoke Traits::value(box);
         return std::forward<Fn>(fn)();

include/beman/monadics/detail/or_else.hpp

@@ -6,7 +6,7 @@
 #include <beman/monadics/detail/get_box_traits.hpp>
 #include <beman/monadics/detail/invoke_with_error.hpp>
 #include <beman/monadics/detail/pipe_adaptor.hpp>
-#include <beman/monadics/detail/rebox_value.hpp>
+#include <beman/monadics/detail/propagate_value.hpp>
 #include <beman/monadics/detail/same_box.hpp>
 
 #include <utility>
@@ -36,7 +36,7 @@ class or_else_t {
             return invoke_with_error(std::forward<Op>(op).callable(key), std::forward<Box>(box));
         }
 
-        return rebox_value<NewBox>(std::forward<Box>(box));
+        return propagate_value<NewBox>(std::forward<Box>(box));
     }
 };
 

include/beman/monadics/detail/propagate_error.hpp

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef BEMAN_MONADICS_DETAIL_PROPAGATE_ERROR_HPP
+#define BEMAN_MONADICS_DETAIL_PROPAGATE_ERROR_HPP
+
+#include <beman/monadics/detail/get_box_traits.hpp>
+#include <beman/monadics/detail/same_box.hpp>
+
+#include <utility>
+
+namespace beman::monadics::detail {
+
+template<typename NewBox, typename Box>
+concept propagatable_error = same_box<NewBox, Box> && (requires {
+    requires has_error_channel<Box>;
+    { get_box_traits<NewBox>::make_error(get_box_traits<Box>::error(std::declval<Box>())) };
+} || requires {
+    requires !has_error_channel<Box>;
+    { get_box_traits<NewBox>::make_error(get_box_traits<Box>::error()) };
+});
+
+template<typename NewBox, typename Box>
+    requires propagatable_error<NewBox, Box>
+[[nodiscard]] constexpr decltype(auto) propagate_error(Box&& box) {
+    using BoxTraits = get_box_traits<Box>;
+    using NewBoxTraits = get_box_traits<NewBox>;
+
+    if constexpr (has_error_channel<Box>) {
+        return NewBoxTraits::make_error(BoxTraits::error(std::forward<Box>(box)));
+    } else {
+        return NewBoxTraits::make_error(BoxTraits::error());
+    }
+}
+
+} // namespace beman::monadics::detail
+
+#endif // BEMAN_MONADICS_DETAIL_PROPAGATE_ERROR_HPP

include/beman/monadics/detail/rebox_value.hpp → include/beman/monadics/detail/propagate_value.hpp

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-#ifndef BEMAN_MONADICS_DETAIL_REBOX_VALUE_HPP
-#define BEMAN_MONADICS_DETAIL_REBOX_VALUE_HPP
+#ifndef BEMAN_MONADICS_DETAIL_PROPAGATE_VALUE_HPP
+#define BEMAN_MONADICS_DETAIL_PROPAGATE_VALUE_HPP
 
 #include <beman/monadics/detail/get_box_traits.hpp>
 #include <beman/monadics/detail/same_box.hpp>
@@ -12,8 +12,16 @@
 namespace beman::monadics::detail {
 
 template<typename NewBox, typename Box>
-    requires same_box<NewBox, Box>
-[[nodiscard]] constexpr decltype(auto) rebox_value(Box&& box) noexcept {
+concept propagatable_value = same_box<NewBox, Box> && (requires {
+    requires std::is_void_v<typename get_box_traits<NewBox>::value_type>;
+    { get_box_traits<NewBox>::make() };
+} || requires {
+    { get_box_traits<NewBox>::make(get_box_traits<Box>::value(std::declval<Box>())) };
+});
+
+template<typename NewBox, typename Box>
+    requires propagatable_value<NewBox, Box>
+[[nodiscard]] constexpr decltype(auto) propagate_value(Box&& box) {
     using BoxTraits = get_box_traits<Box>;
     using NewBoxTraits = get_box_traits<NewBox>;
 
@@ -26,4 +34,4 @@ template<typename NewBox, typename Box>
 
 } // namespace beman::monadics::detail
 
-#endif // BEMAN_MONADICS_DETAIL_REBOX_VALUE_HPP
+#endif // BEMAN_MONADICS_DETAIL_PROPAGATE_VALUE_HPP

include/beman/monadics/detail/transform.hpp

@@ -6,7 +6,7 @@
 #include <beman/monadics/detail/get_box_traits.hpp>
 #include <beman/monadics/detail/invoke_with_value.hpp>
 #include <beman/monadics/detail/pipe_adaptor.hpp>
-#include <beman/monadics/detail/rebox_error.hpp>
+#include <beman/monadics/detail/propagate_error.hpp>
 #include <beman/monadics/detail/same_box.hpp>
 
 #include <type_traits>
@@ -42,7 +42,7 @@ class transform_t {
             }
         }
 
-        return rebox_error<NewBox>(std::forward<Box>(box));
+        return propagate_error<NewBox>(std::forward<Box>(box));
     }
 };
 

include/beman/monadics/detail/transform_error.hpp

@@ -36,7 +36,7 @@ class transform_error_t {
                                                               std::forward<Box>(box)));
         }
 
-        return rebox_value<NewBox>(std::forward<Box>(box));
+        return propagate_value<NewBox>(std::forward<Box>(box));
 
         // gcc11/12 internal crash with pipe_adaptor_t
         // return std::forward<Box>(box) | or_else([f = std::forward<Op>(op).callable(key)](auto&& e) {

include/beman/monadics/monadics.hpp

@@ -6,8 +6,12 @@
 #include <beman/monadics/detail/access_key.hpp>
 #include <beman/monadics/detail/and_then.hpp>
 #include <beman/monadics/detail/get_box_traits.hpp>
+#include <beman/monadics/detail/invoke_with_error.hpp>
+#include <beman/monadics/detail/invoke_with_value.hpp>
 #include <beman/monadics/detail/or_else.hpp>
 #include <beman/monadics/detail/pipe_adaptor.hpp>
+#include <beman/monadics/detail/propagate_error.hpp>
+#include <beman/monadics/detail/propagate_value.hpp>
 #include <beman/monadics/detail/transform.hpp>
 #include <beman/monadics/detail/transform_error.hpp>
 
@@ -20,9 +24,13 @@ using detail::box;
 using detail::box_traits;
 using detail::get_box_traits;
 using detail::has_error_channel;
+using detail::invoke_with_error;
+using detail::invoke_with_value;
 using detail::or_else;
 using detail::or_elseable;
 using detail::pipe_adaptor;
+using detail::propagate_error;
+using detail::propagate_value;
 using detail::transform;
 using detail::transform_error;
 using detail::transform_errorable;

tests/beman/monadics/detail/CMakeLists.txt

@@ -23,8 +23,8 @@ set(tests
     meta_rebind_error
     meta_rebind
     pipe_adaptor
-    rebox_error
-    rebox_value
+    propagate_error
+    propagate_value
     same_box
 )