public void mark() {
        markPos = pos;
    }

    public void next() {
        next(1);
    }

    public void next(int n) {
        pos += n;
    }

    public boolean lookingAt(char c) {
        return input.charAt(pos) == c;
    }

    public boolean lookingAt(CharSequence prefix) {
        int i = 0;
        int cpos = pos;
        while (i < prefix.length() && cpos < input.length()) {