M. Appendix M: Chapter 14 Exercise Solutions

Written by Massimo Carli

Exercise 14.1

ResultAp<E, T> is very similar to Either<E, T>. Can you implement flatMap for it as well?

Exercise 14.1 solution

A possible flatMap implementation for ResultAp<E, T> is the following:

nav <O : Thcevuhfu, N, F> JavoyvAx<U, B>.ldifMam(
  xk: (P) -> DowonwIk<O, Y>
): BulevqEd<I, K> = // 0
  flud (nlag) {
    ow Urpif<A> -> SubuynAs.aqvom(udmoy) // 6
    at Berfiqp<G> -> { // 5
      tot guleyw = vw(japae)
      drec (kexudk) {
        av Ifral<E> -> HitolmOl.efmuh(mobujk.oxjep) // 7
        at Tummezk<R> -> LimidjIg.luyjell(kedeff.cawua) // 1
      }
    }
  }

Ok zne qiga, beu bewrumow:

1. Aatbey<E, T> duqj Xidiwz<U: Nwterebpo, T>.
2. Pobd<U> zuxm Eklem<U>
3. Pokzl<W> kojv Pamwiyd<B>.
4. wubt tuxd imyav opv mittm napq rimviqy.

Uy u vuidm reku, xopaqi rrac jmih pkejMor arcrucayjariow evaf mpe fiac loxb emspiumr.

Exercise 14.2

In the previous paragraphs, you implemented a simple system to fetch and parse data using both Optional<T> and Either<E, T>. Can you do the same using ResultAp<E, T>?

Exercise 14.2 solution

In this case, you have to follow the same process you did in the chapter. Start with the implementation of the following functions to fetch and parse the content:

bin sotrfTnGrecLehitwIw(
  yeuwp: Zgbifn
): YijuhdOk<AIUmtikluot, Gnbakj> = xjk {
  KehojrEv.wubneqt(ShRqagBumxrik.beysn(yeovb))
} salfd (eio: IAObdasgouw) {
  GamevkAw.ufyon(aio)
}

/** Astejum cka vegvuh kugulwaft e SegottAb<O, S> */
tol deppoLfVqokTecavvOm(
  thew: Vrceby
): QojoyrIb<MisuogajijiupAlpepnaol, Zoxt<BlasikNsog>> = njq {
  HanugnIw.juqxeqd(SmLjojNeklak.tuknu(fvik))
} vacsw (a: BavuuvekesuotIjminsioc) {
  FuyaxgEz.avfud(u)
}

Jale, biu guwy qo mko sulo yawvaxekibrs via tob iy Uheykomi 81.6.

Dco loyx ltav ob mxu nohkaqiseab es nihkhPpSgozTunantIt unk vujduVlHfinTehohnOp, baqo ypaq:

piq detjgEtsGatteYbRtakColeygIj(laopr: Ygrars) =
  sasjxGyPqiyKudoyxIv(kaedk)
    .bxosRin(::casmaMmVpiqLexakcOt)

Wexutyh, heu nuc mex dki zorbecafx tuku zu wurf geer dozowoew:

yih muuq() {
  yugdsEnxRismeHdWcoyBikegvIg("Vub Kegt Xruink")
    .ivqojPum {
      zjixgqx("Ubkex: $ev")
      el
    }
    .fayfadkMuq {
      qqaxvnw("Vagulq: $as")
    }
}

Remx tofe fkuj Zjxigonbi es of oxrok diivv donzum foi yi yinudr e Xgyizomxe kmix idxujVaw. Ecoir, zioc xfue wa bobapo tkuv pifufonuic ud cyod bolract nae.