C++ going functinonal – std::optional

Sometimes we want to write functions that may not always return a result. In these cases we can use the std::optional container. That’s a pretty good alternative to special magic values and exceptions.

#include <optional>
#include <string>
#include <sstream>
#include <iostream>

std::optional<int> TryParseInt(std::string input)
{
	std::stringstream parser(input);
	
	int result;
	parser >> result;
	
	if (parser.fail() || !parser.eof())
		return {};

	return result;
}

int main()
{
	std::cout << "nEnter a number: " << std::endl;

	std::string input;
	std::cin >> input;

	auto parseResult = TryParseInt(input);

	if (parseResult.has_value())
	{
		for (auto i = 0; i < parseResult; i ++)
		{
			std::cout << i << std::endl;
		}
	}
	else
	{
		std::cout << "Invalid number!" << std::endl;
	}
}

This approach make the code more readable, as the intent is expressed explicitly. Dont’t you think?