std::string stripnonalp(std::string input_string)
{
    std::string output_string = "";
    bool lastwasspace = 0;

    for (char current_letter : input_string)
    {
        current_letter = tolower(current_letter);

        if (lastwasspace == false)
        {
            if((current_letter == ' ') || (current_letter == '\n') || (current_letter == '\r'))
            {
                lastwasspace = true;
                output_string += " ";
            }

            if(current_letter == '\'')
                output_string += "'";

            if((current_letter >= 'a') && (current_letter <= 'z'))
                output_string += current_letter;
        }


        if (lastwasspace == true)
        {
            if(current_letter == '\'')
            {
                output_string += "'";
                lastwasspace = false;
            }

            if((current_letter >= 'a') && (current_letter <= 'z'))
            {
                output_string += current_letter;
                lastwasspace = false;
            }
        }
    }
    return output_string;
}