const rfc1123Date: PS.Parser<HttpDate> = PS.co(function *() {
  yield PS.optional(weekDay.chain(() => PS.string(', ')));
  const [y, m, d]: [number, Month, Day] = yield date;
  yield PS.optional(PS.whiteSpace);
  const [h, n, s]: [number, number, number] = yield time;
  yield PS.optional(PS.whiteSpace);
  // RFC 2616 defines GMT only but there are actually ill-formed ones such
  // as "+0000" and "UTC" in the wild.
  yield PS.string('GMT').alt(PS.string('+0000')).alt(PS.string('UTC'));

  return PS.pure(fromDate(new Date(Date.UTC(y, m, d, h, n, s))));
});

)).alt(PS.attempt(PS.co(function* () {
  const a1: string = yield optNH4cH4(0);
  yield PS.string('::');
  const a2: string = yield countP(4, h4c).map(arrjoinStr);
  const a3: string = yield ls32;
  return PS.pure(`${a1}::${a2}${a3}`);
}))).alt(PS.attempt(PS.co(function* () {

const hierPart: PS.Parser<[Maybe<URIAuth>, string]> = PS.co(function* () {
  yield PS.attempt(PS.string('//'));
  const ua: Maybe<URIAuth> = yield uauthority;
  const up: string = yield pathAbEmpty;
  return PS.pure([ua, up]);
})

 yield PS.optional(weekDay.chain(() => PS.string(', ')));