From 20f8a49801f050edfc78a8dc3d01c0373f81d918 Mon Sep 17 00:00:00 2001
From: Ben Deane <ben@elbeno.com>
Date: Fri, 11 Sep 2026 16:48:03 -0600
Subject: [PATCH] :sparkles: Add functionality for named types

Problem:
- Named types are used everywhere, but in an ad-hoc manner.

Solution:
- Add `named` concept to detect a the `name` of a type as well as `name_of_v`
  and `constant_name_of_v` to extract the name either as a `ct_string` or a
  `cts_t`.
- Add `with_name` as a convenient "named type" base class.
---
 include/stdx/ct_string.hpp | 20 ++++++++++++++++++++
 test/ct_string.cpp         |  8 ++++++++
 test/tuple_algorithms.cpp  | 26 +++++++++++---------------
 3 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/include/stdx/ct_string.hpp b/include/stdx/ct_string.hpp
index 0881b9e..7f7cf29 100644
--- a/include/stdx/ct_string.hpp
+++ b/include/stdx/ct_string.hpp
@@ -182,5 +182,25 @@ template <ct_string S> consteval auto operator""_cts() { return S; }
 template <ct_string S> consteval auto operator""_ctst() { return cts_t<S>{}; }
 } // namespace ct_string_literals
 } // namespace literals
+
+template <ct_string Name> struct with_name {
+    constexpr static auto name = Name;
+    friend constexpr auto operator==(with_name, with_name) -> bool = default;
+};
+
+namespace detail {
+template <typename T>
+concept is_ct_string =
+    stdx::is_value_specialization_of_v<std::remove_cvref_t<T>, ct_string>;
+}
+
+template <typename T>
+concept named = requires {
+    { T::name } -> detail::is_ct_string;
+};
+
+template <named T> constexpr auto name_of_v = T::name;
+template <named T> using constant_name_of_t = cts_t<T::name>;
+template <named T> constexpr auto constant_name_of_v = constant_name_of_t<T>{};
 } // namespace v1
 } // namespace stdx
diff --git a/test/ct_string.cpp b/test/ct_string.cpp
index f9b16a0..43f82c5 100644
--- a/test/ct_string.cpp
+++ b/test/ct_string.cpp
@@ -192,3 +192,11 @@ TEST_CASE("CT_WRAP", "[ct_string]") {
         STATIC_REQUIRE(CT_WRAP(X) == "hello"_ctst);
     }.template operator()<"hello">();
 }
+
+TEST_CASE("named object", "[ct_string]") {
+    using namespace stdx::ct_string_literals;
+    using T = stdx::with_name<"test">;
+    STATIC_CHECK(stdx::named<T>);
+    STATIC_CHECK(stdx::name_of_v<T> == "test"_cts);
+    STATIC_CHECK(stdx::constant_name_of_v<T> == "test"_ctst);
+}
diff --git a/test/tuple_algorithms.cpp b/test/tuple_algorithms.cpp
index e3732f1..d0dc7c4 100644
--- a/test/tuple_algorithms.cpp
+++ b/test/tuple_algorithms.cpp
@@ -1,5 +1,6 @@
 #include "detail/tuple_types.hpp"
 
+#include <stdx/ct_string.hpp>
 #include <stdx/span.hpp>
 #include <stdx/tuple_algorithms.hpp>
 #include <stdx/utility.hpp>
@@ -979,31 +980,26 @@ TEST_CASE("gather with move only types", "[tuple_algorithms]") {
 }
 
 namespace {
-template <typename T> struct named_int {
-    using name_t = T;
+template <stdx::ct_string Name> struct named_int : stdx::with_name<Name> {
+    constexpr named_int(int v) : value{v} {}
     int value;
     friend constexpr auto operator==(named_int, named_int) -> bool = default;
 };
-
-template <typename T> using name_of_t = typename T::name_t;
 } // namespace
 
 TEST_CASE("gather_by with projection", "[tuple_algorithms]") {
-    struct A;
-    struct B;
-    struct C;
-    constexpr auto t = stdx::tuple{named_int<C>{3}, named_int<B>{11},
-                                   named_int<A>{0}, named_int<B>{12}};
-    constexpr auto gathered = stdx::gather_by<name_of_t>(t);
+    constexpr auto t = stdx::tuple{named_int<"C">{3}, named_int<"B">{11},
+                                   named_int<"A">{0}, named_int<"B">{12}};
+    constexpr auto gathered = stdx::gather_by<stdx::constant_name_of_t>(t);
     STATIC_REQUIRE(
         std::is_same_v<decltype(gathered),
-                       stdx::tuple<stdx::tuple<named_int<A>>,
-                                   stdx::tuple<named_int<B>, named_int<B>>,
-                                   stdx::tuple<named_int<C>>> const>);
-    CHECK(get<0>(gathered) == stdx::tuple{named_int<A>{0}});
+                       stdx::tuple<stdx::tuple<named_int<"A">>,
+                                   stdx::tuple<named_int<"B">, named_int<"B">>,
+                                   stdx::tuple<named_int<"C">>> const>);
+    CHECK(get<0>(gathered) == stdx::tuple{named_int<"A">{0}});
     CHECK(stdx::get<1>(gathered).fold_left(
               0, [](auto x, auto y) { return x + y.value; }) == 23);
-    CHECK(get<2>(gathered) == stdx::tuple{named_int<C>{3}});
+    CHECK(get<2>(gathered) == stdx::tuple{named_int<"C">{3}});
 }
 
 TEST_CASE("tuple_cons", "[tuple_algorithms]") {