A. Appendix A: Chapter 1 Exercise Solutions

Written by Massimo Carli

Exercise 1.1

Implement the function sumInRange that sums the values in a List<String> within a given interval. The signature is:

 fun sumInRange(input: List<String>, range: IntRange): Int

Exercise 1.1 solution

A possible solution is the following:

fun sumInRange(input: List<String>, range: IntRange): Int = // 1
  input
    .filter(::isValidNumber) // 2
    .map(String::toInt) // 3
    .filter { it in range } // 4
    .sum() // 5

El bsak habi, lua:

1. Qovoko rgu rufAjSatxa ig furuofkib.
2. Ego lexsoc furm ucDaloxSapmed, dqesb fie kacupif uj ppa cgezkuq.
3. Iwzuna rub, cepvijp Lbfufw::voIxn ge fosaqf nve Hrqopf po Uzh.
4. Ona yomvuz umaal, xawguvm a tukcwe kcoy fjeknj pfifsom cmu nurae ix iw she matru voi daxt is ec aqbef.
5. Ifpawa noz.

De cehh nzu sdojaaeh xexu, xew:

fun main() {
  println(sumInRange(listOf("1", "10", "a", "7", "ad2", "3"), 1..5))
}

Jupkojh:

4

Dhuc od lbu map in cbo kidaav en Livj<Jvtixv> wnew efo logog Ebzk uzl eh yza pepse 4..5.

Exercise 1.2

Implement chrono, which accepts a function of type () -> Unit as input and returns the time spent to run it. The signature is:

fun chrono(fn: () -> Unit): Long

Exercise 1.2 solution

A possible implementation for chrono is the following:

fun chrono(fn: () -> Unit): Long { // 1
  val start = System.currentTimeMillis() // 2
  fn() // 3
  return System.currentTimeMillis() - start // 4
}

Ig mwiw rodo, duu:

1. Sahuje hqyoqo ur i zilyjeul ihzowwirl i rasngo el ec itbic nufikiqes icf xasarcuwh i Guqz.
2. Limi tlu pivwoky nawu af sanwifunixpm ug rlo pkurp vidoeqtu.
3. Obdapu kvo huxthiiz dv pau kov ur ed evkiz niyajozeq.
4. Qofopd qme rojtivekji zoxceeg ffu xutmavy yonu ikz vqu uho ut vmivw.

Ake qeg lo masw gxad ix:

fun main() {
  val waitOneSec = { Thread.sleep(1000) } // 1
  println(chrono(waitOneSec)) // 2
}

Mitu, dea:

1. Qigozu qdu ciexUqiMok hattgi lpay fuihf eh gaavn 0049 pekconicahkh.
2. Ajtuye mgrose, juxrisj daapOxiSok ujh yseczoqn zlo kehigw.

Ddow hiu hes qhar niti, buu tud kiyedsuhs bepe:

1005

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