gistfile1.cs

private T ParseOneOf<T>(params Func<T>[] fs) {
    var oldLexer = Lexer.Clone();
    foreach (var f in fs) {
        try {
            return f();
        } catch (SyntaxErrorException) {
            Lexer = oldLexer;
        }
    }
    throw new SyntaxErrorException();
}

private IEnumerable<T> ParseMany<T>(Func<T> f) {
    for (; ; ) {
        var oldLexer = Lexer.Clone();
        T v = default(T);
        try {
            v = f();
        } catch (SyntaxErrorException) {
            Lexer = oldLexer;
            yield break;
        }
        yield return v;
    }
}