import ParserCombinator


// Basic token parser – converts a symbol from input stream into an integer
let number: Parser<String, Int> = %"number" => { num in Int(num)! }

// Declaration for the recursive reference
let expr: Parser<String, Int>

// Here we reference future value of expn
let factor =
        (§"(" *> wrap { expr } <* §")")
        || number

let term   =
        (factor + (§"*" *> factor))      => (*)
        || (factor + (§"/" *> factor))   => (/)
        || factor

// Definition of the
expr   =
        (term + (§"+" *> term))      => (+)
        || (term + (§"-" *> term))   => (-)
        || term

let parser = expr

let source = ["1", "+", "2", "*", "(", "3", "+","4", ")"].stream()

let result = parser.parse(source)