COMPILE-TIME KEYWORD-TO-TOKEN CATEGORIZATION SYSTEM - This code comes from an unfinished project of mine. I found certain parts quite interesting, so I extracted a few of them and turned them into gists. This code is for educational purposes and is not functional, as it requires the rest of the architecture to work.

compile-time-token-keyword-categorizer.cppm

// Copyright (c) July 2026 Félix-Olivier Dumas. All rights reserved.
// Licensed under the terms described in the LICENSE file

	template<typename entry_tuple>
	struct TokenKeywordCategorizerConfigurationSchema {
		using first_t = std::decay_t<std::tuple_element_t<0, entry_tuple>>;
		using second_t = std::decay_t<std::tuple_element_t<1, entry_tuple>>;

		static constexpr bool valid =
			requires {
				requires std::tuple_size_v<entry_tuple> == 2;

				requires is_keyword_matching_policy<first_t>;
				requires std::is_same_v<std::decay_t<decltype(second_t::value)>, TokenKind>;
			};
	};

	template<typename entry_tuple>
	struct TokenKeywordCategorizerConfigurationModel final {
		using predicate = std::tuple_element_t<0, entry_tuple>;
		static constexpr TokenKind corresponding = std::tuple_element_t<1, entry_tuple>::value;
	};

	template<typename... Entries>
	using TokenKeywordCategorizerConfiguration = ConfigurationSystem<
		TokenKeywordCategorizerConfigurationSchema,
		TokenKeywordCategorizerConfigurationModel,
		Entries...
	>;

	template <typename T>
	constexpr bool is_token_keyword_categorizer_config_v = false;

	template <typename... Entries>
	constexpr bool is_token_keyword_categorizer_config_v<TokenKeywordCategorizerConfiguration<Entries...>> = true;

	template <typename T>
	concept is_token_keyword_categorizer_configuration = is_token_keyword_categorizer_config_v<T>;

	// ca se répète souvent, y'aurais peut-être moyen de factoriser tout cela de facon a rendre la chose plus lisible



	export template<is_token_keyword_categorizer_configuration Configuration>
	struct TokenKeywordCategorizer final {
	protected:
		using configuration_tuple_t = typename Configuration::type;

		static constexpr bool is_nothrow_config = []<typename... Ts>(std::type_identity<std::tuple<Ts...>>) {
			return (noexcept(Ts::predicate::matches(std::string_view{})) && ...);
		}(std::type_identity<configuration_tuple_t>{});

	public:
		[[nodiscard]] static constexpr TokenKind transform(std::string_view sv) noexcept(is_nothrow_config) {
			return [&]<typename... Ts>(std::type_identity<std::tuple<Ts...>>) {
				TokenKind result = TokenKind::Unknown;
				(((Ts::predicate::matches(sv)) && (result = Ts::corresponding, true)), ...);

				return result;
			}(std::type_identity<configuration_tuple_t>{});
		}
	};