Merge pull request #250 from elbeno/cx-strings

🎨 Make `cts_t` and `format_result` easier to format

Author: elbeno

include/stdx/ct_format.hpp

@@ -51,6 +51,24 @@ template <typename Str, typename Args> struct format_result {
                                      format_result const &) -> bool = default;
 };
 
+template <typename Str, typename Args>
+    requires(Args::size() == 0 and is_cx_value_v<Str>)
+struct format_result<Str, Args> {
+    CONSTEVAL static auto ct_string_convertible() -> std::true_type;
+
+    [[no_unique_address]] Str str;
+    [[no_unique_address]] Args args{};
+
+    friend constexpr auto operator+(format_result const &fr) { return +fr.str; }
+
+    constexpr auto operator()() const noexcept { return +(*this); }
+    using cx_value_t [[maybe_unused]] = void;
+
+  private:
+    friend constexpr auto operator==(format_result const &,
+                                     format_result const &) -> bool = default;
+};
+
 template <typename Str, typename Args>
 format_result(Str, Args) -> format_result<Str, Args>;
 template <typename Str> format_result(Str) -> format_result<Str, tuple<>>;

include/stdx/ct_string.hpp

@@ -145,6 +145,8 @@ template <ct_string S> struct cts_t {
 
     CONSTEVAL static auto ct_string_convertible() -> std::true_type;
     friend constexpr auto operator+(cts_t const &) { return value; }
+    constexpr auto operator()() const noexcept { return value; }
+    using cx_value_t [[maybe_unused]] = void;
 };
 
 template <ct_string X, ct_string Y>

include/stdx/type_traits.hpp

@@ -274,6 +274,5 @@ STDX_PRAGMA(diagnostic pop)
 template <typename T, typename = void> constexpr auto is_complete_v = false;
 template <typename T>
 constexpr auto is_complete_v<T, detail::void_v<sizeof(T)>> = true;
-
 } // namespace v1
 } // namespace stdx

test/ct_format.cpp

@@ -263,11 +263,21 @@ TEST_CASE("FORMAT a type argument", "[ct_format]") {
     STATIC_REQUIRE(STDX_CT_FORMAT("Hello {}", int) == "Hello int"_fmt_res);
 }
 
-TEST_CASE("FORMAT a constexpr string argument", "[ct_format]") {
+TEST_CASE("FORMAT a constexpr ct_string argument", "[ct_format]") {
     constexpr static auto S = "world"_cts;
     STATIC_REQUIRE(STDX_CT_FORMAT("Hello {}", S) == "Hello world"_fmt_res);
 }
 
+TEST_CASE("FORMAT a cts_t argument", "[ct_format]") {
+    auto S = "world"_ctst;
+    STATIC_REQUIRE(STDX_CT_FORMAT("Hello {}", S) == "Hello world"_fmt_res);
+}
+
+TEST_CASE("FORMAT a format_result argument", "[ct_format]") {
+    auto S = "world"_fmt_res;
+    STATIC_REQUIRE(STDX_CT_FORMAT("Hello {}", S) == "Hello world"_fmt_res);
+}
+
 TEST_CASE("FORMAT a constexpr int argument", "[ct_format]") {
     constexpr static auto I = 17;
     STATIC_REQUIRE(STDX_CT_FORMAT("Hello {}", I) == "Hello 17"_fmt_res);