Function int

Just like Simple.int where you have to handle negation yourself. The only difference is that you provide two potential problems:

const int =
<PROBLEM>(expecting: PROBLEM) =>
(invalid: PROBLEM): Parser<PROBLEM, number> => {
  return number({
    int: Ok((id: number) => id),
    hex: Err(invalid),
    octal: Err(invalid),
    binary: Err(invalid),
    float: Err(invalid),
    invalid: invalid,
    expecting: expecting,
  });
};

You can use problems like ExpectingInt and InvalidNumber.