Simple parser combinator in Swift

Parser.swift

typealias Parser = String -> (String, String)

func charParser(char: Character) -> Parser {
    return { text in
        if text[text.startIndex] == char {
            return (String(char), text[advance(text.startIndex, 1)..<text.endIndex])
        }
        return ("", text)
    }
}

infix operator <|> { associativity left precedence 110 }
func <|>(left: Parser, right: Parser) -> Parser {
    return { text in
        let result = left(text)
        if result.0.isEmpty {
            return right(text)
        }
        return result
    }
}

infix operator <&> { associativity left precedence 120 }
func <&>(left: Parser, right: Parser) -> Parser {
    return { text in
        let leftResult = left(text)
        let rightResult = right(leftResult.1)
        return (leftResult.0 + rightResult.0, rightResult.1)
    }
}

let aParser = charParser("a")
let bParser = charParser("b")
let cParser = charParser("c")
let hogeParser = charParser("?")
let parser = aParser <&> bParser <&> (cParser <|> hogeParser)
parser("abcde") //=> ("abc", "de")