Console Calculator 2000

cc2000.rb

# could be shorter or better implemented, but this'll do for now :)

class String
    def is_numeric?
        Rational(self) != nil rescue false
    end
end

def parse(input)
    if input.kind_of? String
        if input.is_numeric?
            input.to_r
        else
            test_validity(input)
        end
        
    elsif input.kind_of? Array
        input.each do |inner|
            operations = ["-", "+", "/", "*"]
            
            operations.each do |operation|
                if inner.include? operation
                    return inner\
                        .split(operation)\
                        .map { |e| parse(e) }\
                        .reduce do |a, b|
                            case operation
                            when "-" then a - b
                            when "+" then a + b
                            when "/" then a / b
                            when "*" then a * b
                            end
                        end
                end
            end
            
            return "invalid operation sequence detected, please use NONONON... sequence, (N)umber, (O)peration, it must end with a number"
        end
    end
end

def test_validity(input)
    if input =~ /[\d\+\-\*\/ ]/
        parse([input])
    else
        "input is invalid, non-number or unidentified characters detected"
    end
end

def main
    puts "Welcome to Console Calculator 2000"
    
    prompt = "> "
    while true
        output = ""
        
        print prompt
        
        input = gets.chomp
        
        parsed_input = parse(input)
        parsed_input = parsed_input.to_f.to_s if parsed_input.kind_of? Numeric
        
        output += parsed_input
        
        puts "\u001b[1000D#{output}"
    end
end

main()