change trampolining to avoid instantiation and add fixed_string alias

Author: Hana Dusíková

include/ctll/parser.hpp

@@ -15,6 +15,10 @@ enum class decision {
 	undecided
 };
 
+template <typename T> void id(T);
+
+struct placeholder { };
+
 #if !__cpp_nontype_template_parameter_class
 template <typename Grammar, const auto & input, typename ActionSelector = empty_actions, bool IgnoreUnknownActions = false> struct parser {
 #else
@@ -25,8 +29,6 @@ template <typename Grammar, basic_fixed_string input, typename ActionSelector =
 
 	template <size_t Pos, typename Stack = void, typename Subject = void, decision Decision = decision::undecided> struct seed;
 
-	template <size_t Pos> struct placeholder { };
-	
 	template <size_t Pos> static constexpr auto get_current_term() noexcept {
 		if constexpr (Pos < input.size()) {
 			return term<input[Pos]>{};
@@ -107,6 +109,7 @@ template <typename Grammar, basic_fixed_string input, typename ActionSelector =
 		}
 	}
 	// helper type for trampoline
+	
 	template <size_t Pos, typename Stack, typename Subject, decision Decision> struct seed {
 		constexpr inline CTLL_FORCE_INLINE operator bool() const noexcept {
 			return Decision == decision::accept;
@@ -119,22 +122,26 @@ template <typename Grammar, basic_fixed_string input, typename ActionSelector =
 			return decide<Pos>(Stack{}, Subject{});
 		}
 
-		template <size_t RPos> constexpr auto operator+(placeholder<RPos>) const noexcept {
+		constexpr auto operator+(placeholder) const noexcept {
 			if constexpr (Decision == decision::undecided) {
 				// parse for current char (RPos) with previous stack and subject :)
-				return decltype(seed<RPos, Stack, Subject, Decision>::parse()){};
+				return decltype(seed<Pos, Stack, Subject, Decision>::parse()){};
 			} else {
 				// if there is decision already => just push it to the end of fold expression
 				return *this;
 			}
 		}
 	};
 
+	template <size_t> using index_placeholder = placeholder;
+	
 	// trampolines with folded expression
 	template <typename Subject, size_t... Pos> static constexpr auto trampoline_decide(Subject, std::index_sequence<Pos...>) noexcept {
 		// parse everything for first char and than for next and next ...
 		// Pos+1 is needed as we want to finish calculation with epsilons on stack
-		return (seed<0, decltype(grammar.start_stack), Subject, decision::undecided>::parse() + ... + placeholder<Pos+1>());
+		auto v = (seed<0, decltype(grammar.start_stack), Subject, decision::undecided>::parse() + ... + index_placeholder<Pos+1>());
+		//id(v);
+		return v;
 	}
 
 	template <typename Subject = empty_subject> static constexpr auto trampoline_decide(Subject subject = {}) noexcept {

include/ctre/functions.hpp

@@ -19,6 +19,15 @@ template <typename CharT, size_t N> class pattern: public ctll::basic_fixed_stri
 
 template <typename CharT, size_t N> pattern(const CharT (&)[N]) -> pattern<CharT, N>;
 
+// for better examples
+template <typename CharT, size_t N> class fixed_string: public ctll::basic_fixed_string<CharT, N> {
+	using parent = ctll::basic_fixed_string<CharT, N>;
+public:
+	constexpr fixed_string(const CharT (&input)[N]) noexcept: parent(input) { }
+};
+
+template <typename CharT, size_t N> fixed_string(const CharT (&)[N]) -> fixed_string<CharT, N>;
+
 #if __cpp_nontype_template_parameter_class
 template <basic_fixed_string input> CTRE_FLATTEN constexpr CTRE_FORCE_INLINE auto re() noexcept {
 #else

test.cpp

@@ -4,26 +4,12 @@
 #include <iostream>
 
 
-void match(std::string_view subject) {
-	using namespace ctre::literals;
-	
-	if (auto [matched, inner] = "^([0-9]+?[a-z]++)+"_ctre.match(subject); matched) {
-		std::cout << "matched = " << matched.to_view() << "\n";
-		if (inner) {
-			std::cout << "  inner = " << inner.to_view() << "\n";
-		}
-	}
+static constexpr ctre::pattern pattern = "(?:hello|cau|guten tag|ola)|(?:hello|cau|guten tag|ola)|(?:hello|cau|guten tag|ola)|(?:hello|cau|guten tag|ola)|(?:hello|cau|guten tag|ola)|(?:hello|cau|guten tag|ola)|(?:hello|cau|guten tag|ola)";
+
+bool fnc(std::string_view view) {
+	return ctre::match<pattern>(view);
 }
 
 int main() {
-	using namespace std::string_view_literals;
-	match("123abc456def"sv);
-	
-	auto input = "123,456,768"sv;
-	
-	using namespace ctre::literals;
-	for (auto match: ctre::range(input,"[0-9]++"_ctre)) {
-		std::cout << std::string_view{match} << "\n";
-	}
-	
+	std::cout << fnc("hello") << "\n";
 }