#include <vector>
#include <string>

int main()
{

    Alternate variable_parser
    {
        {
            // Match { "x" },
            // Match { "y" }
        }
    };

    Alternate operator_parser
    {
        {
            // Match { "+" },
            // Match { "-" }
        }
    };
    
    Sequence basic_parser
    {
        {
            variable_parser.clone(),
            operator_parser.clone(),
            variable_parser.clone()
        }
    };

    Sequence parenthesis_parser
    {
        {
            // Match { "(" },
            basic_parser.clone(),
            // Match { ")" }
        }
    };

    Sequence single_parenthesis_parser
    {
        {
            // Match { "(" },
            variable_parser.clone(),
            // Match { ")" }
        }
    };
    
    Alternate expression_parser
    {
        {
            parenthesis_parser.clone(),
            single_parenthesis_parser.clone(),
            basic_parser.clone()
        }
    };          
    
    std::string line;
    while (std::getline(std::cin, line))
    {
        std::string::const_iterator current { std::cbegin(line) };
        if (expression_parser.parse(current, std::cend(line)))
        {
            std::cout << "Matched!" << std::endl;
        }
        else
        {
            std::cout << "Didn't match!" << std::endl;
        }
    }
    
}