Some parser thing in Dart

parser.dart

foo(stream) {
    if (stream.lookahead("if")) {
        var ifNode = stream.consume("if");
        var elseIfNode = stream.maybe("else if") || stream.maybe("poop")
    }
}

var dot = (str) => str.consume(".");
var minus = (str) => str.consume("-");
var parseIf = (str) => str.consume("if");
var parseElse = (str) => str.consume("else");

// Use a generator to collect?
digits = new TokenGenerator((str) sync* {
    while(str.peek().isNumber())
        yield str.next();
})

// Parse in sequence
var parseElseIf = parseElse + parseIf;

// Parse maybe
var parseElseMaybeIf = parseElse + maybe(parseIf)

// Parse thrice
var parseElseIfIfIf = parseElse + ntimes(parseIf, 3)

// Parse unlimited
var soManyDots = unlimited(dot);

// Parse an integer or floating point
var floatingPoint = maybe(minus) + digits + dot + digits;
var integer = maybe(minus) + digits;
var number = integer | floatingPoint;

main() async {
    var file = new File("foo.bar");
    var stream = file.openRead().transform(TokenStream.create(skip: [
        " ",
        "\n",
        "\r",
        "\r\n"
    ]));
    var alternatives = [parseIf, parseElse, parseElseIfIfIf, number];

    // "first" finds any of the alternatives
    // var candidates = stream.first(alternatives);

    // Use "next" to select largest token
    var token = stream.next(alternatives);

    if (token == null) {
        // Error reporting isn't so hard, either :)
        print("Error at foo.bar:${stream.position} - Expected ${getNames(alternatives)}");
    } else {
        print("First available token: ${token.text}");
    }
}