decode-line.sc

import shapeless.ops.hlist.{Length, Repeat}
import shapeless.{::, Generic, HList, HNil, Nat}

case class IceCream(name: String, numCherries: Int, inCone: Boolean)

def repeat[I <: HList, L <: Nat, O <: HList](in: I, s: String)(
  implicit
    len: Length.Aux[I, L],
    rep: Repeat.Aux[String :: HNil, L, O]
): O = rep(s :: HNil)

def extract[A](start: Int, end: Int, convert: String => A): String => A =
  line => convert(line.substring(start - 1, end).trim)

val extractors =
  extract(1,  12, identity)   ::
  extract(13, 14, _.toInt)    ::
  extract(15, 17, _ == "yes") ::
  HNil

def lineToIceCream(line: String): IceCream =
  Generic[IceCream].from(extractors zipApply repeat(extractors, line))

val lines = List (
    "Sundae       1no ",  // IceCream(Sundae,       1,  false),
    "Cornetto    13yes",  // IceCream(Cornetto,     13, true),
    "Banana Split 0no ")  // IceCream(Banana Split, 0,  false)
  .map(lineToIceCream)