Variadic templates to find types

template.cpp

#include <string>
#include <vector>
#include <iostream>
#include <type_traits>

using namespace std;

template<typename T>
string GetArgumentType() {
	if (std::is_same<T, int>()) {
		return "INT";
	} else if (std::is_same<T, double>()) {
		return "DOUBLE";
	} else {
		// unrecognized type
		throw std::exception();
	}
}

template <typename TA>
void GetArgumentTypesRecursive(vector<string> &arguments) {
	arguments.push_back(GetArgumentType<TA>());
}

template<typename TA, typename TB, typename... Args>
void GetArgumentTypesRecursive(vector<string> &arguments) {
	arguments.push_back(GetArgumentType<TA>());
	GetArgumentTypesRecursive<TB, Args...>(arguments);
}


template<typename TA, typename... Args>
void PrintTypes(string function_name) {
	vector<string> arguments;
	GetArgumentTypesRecursive<TA, Args...>(arguments);

	if (arguments.size() < 1) {
		cout << "at least one template (return type) is required!\n";
		throw std::exception();
	}

	// first one is return type
	cout << function_name << "(";
	for(int i = 1; i < arguments.size(); i++) {
		if (i > 1) {
			cout << ", ";
		}
		cout << arguments[i];
	}
	cout << ") -> " << arguments[0] << "\n";

}

int main() {
	// first param is return type:

	// udf() -> INT
	PrintTypes<int>("udf");
	// udf(DOUBLE, DOUBLE) -> INT
	PrintTypes<int, double, double>("udf");
	// udf(INT, DOUBLE, INT) -> INT
	PrintTypes<int, int, double, int>("udf");
}