pub fn and_then<P, F, O, E, I>(p: P, f: F) -> AndThen<P, F>where P: Parser<Input = I>, F: FnMut(P::Output) -> Result<O, E>, I: Stream, E: Into<<I::Error as ParseError<I::Item, I::Range, I::Position>>::StreamError>,
Equivalent to p.and_then(f).
p.and_then(f)