Keskustelu: Ohjelmointikysymykset: C++: laskin

#include <cmath>
#include <iostream>
#include <stdexcept>

double laske(const double a = 0, const char m = '+', const double b = 0)
throw(std::domain_error, std::invalid_argument) {
	switch (m) {
		case '+': return a+b;
		case '-': return a-b;
		case '*': return a*b;
		case '/': if (!a*!b) throw std::domain_error("0/0 ei onnistu");
			return a/b;
		case '^': if (!a*!b) throw std::domain_error("0^0 ei onnistu");
			return std::pow(a,b);
		default: throw std::invalid_argument(std::string() + m);
	}
}

int main()
try {
	double a, b; char m;
	if (!(std::cin >> a >> m >> b)) {
		throw std::runtime_error("virhe: anna lasku esim 12.3 + 45.6");
	}
	std::cout << laske((a, m, b)) << std::endl;
} catch (std::invalid_argument &e) {
	std::cout << "virhe parametreissa: tuntematon lasku: " << e.what() << std::endl;
	return 1;
} catch (std::domain_error &e) {
	std::cout << "virhe luvuissa: " << e.what() << std::endl;
	return 1;
} catch (std::runtime_error &e) {
	std::cout << e.what() << std::endl;
	return 1;
}