feat: basically finish parser helper.

- basically finish parser helper, including TryParse, Parse and ToString.
- only Parse has been tested. other test should be filled in future.

src/ParserHelper.hpp

@@ -1,10 +1,84 @@
 #pragma once
+#include "YYCCInternal.hpp"
+
+#include "EncodingHelper.hpp"
 #include <string>
 #include <cinttypes>
+#include <type_traits>
+#include <stdexcept>
+#include <limits>
 
 namespace YYCC::ParserHelper {
 
-	bool Parse(const std::string& strl, int& ret, int base = 10);
-	int Parse(const std::string& strl, int base = 10);
+	template<class>
+	constexpr bool g_AlwaysFalse = false;
+
+	template<typename _Ty, std::enable_if_t<std::is_floating_point_v<_Ty>, int> = 0>
+	bool TryParse(const std::string& strl, _Ty& num) {
+		try {
+			// float types
+			if constexpr (std::is_same_v<_Ty, float>) {
+				num = std::stof(strl, nullptr);
+			} else if constexpr (std::is_same_v<_Ty, double>) {
+				num = std::stod(strl, nullptr);
+			} else if constexpr (std::is_same_v<_Ty, long double>) {
+				num = std::stold(strl, nullptr);
+			} else {
+				static_assert(g_AlwaysFalse<_Ty>, "Invalid float type.");
+			}
+			return true;
+		} catch (const std::invalid_argument&) {
+			return false;
+		} catch (const std::out_of_range&) {
+			return false;
+		}
+	}
+	template<typename _Ty, std::enable_if_t<std::is_integral_v<_Ty> && !std::is_same_v<_Ty, bool>, int> = 0>
+	bool TryParse(const std::string& strl, _Ty& num, int base = 10) {
+		try {
+			// integer type
+			// decide integer type
+			using container_t = std::conditional_t<std::is_unsigned_v<_Ty>, unsigned long long, long long>;
+			// parse it from string according to whether integer type is signed.
+			container_t cache;
+			if constexpr (std::is_unsigned_v<_Ty>) {
+				cache = std::stoull(strl, nullptr, base);
+			} else {
+				cache = std::stoll(strl, nullptr, base);
+			}
+			// check its range
+			if (cache < std::numeric_limits<_Ty>::min() || cache > std::numeric_limits<_Ty>::max())
+				return false;
+			num = static_cast<_Ty>(cache);
+			return true;
+		} catch (const std::invalid_argument&) {
+			return false;
+		} catch (const std::out_of_range&) {
+			return false;
+		}
+	}
+	bool TryParse(const std::string& strl, bool& num) {
+		if (strl == "true") num = true;
+		else if (strl == "false") num = false;
+		else return false;
+		return true;
+	}
+
+	template<typename _Ty, std::enable_if_t<std::is_arithmetic_v<_Ty>, int> = 0>
+	_Ty Parse(const std::string& strl) {
+		_Ty ret;
+		TryParse(strl, ret);
+		return ret;
+	}
+
+	template<typename _Ty, std::enable_if_t<std::is_arithmetic_v<_Ty>, int> = 0>
+	std::string ToString(_Ty num) {
+		return std::to_string(num);
+	}
+	template<>
+	std::string ToString<bool>(bool num) {
+		if (num) return std::string("true");
+		else return std::string("false");
+	}
 
 }