Scala - Core Scala - Common Collections(string list, palindromes, operations( partition, foldLeft))

Learning Scala:
Practical Functional Programming for the JVM
(O'Reilly Media)
Jason Swartz (著)

開発環境

• OS X El Capitan - Apple (OS)
• Emacs (Text Editor)
• Scala (プログラミング言語)

Learning Scala: Practical Functional Programming for the JVM (Jason Swartz (著)、O'Reilly Media)のPart Ⅰ. (Core Scala)、Chapter 6.(Common Collections)、Exercises 6.(No. 2481)を解いてみる。

その他参考書籍

• Programming Scala: Scalability = Functional Programming + Objects

Exercises 6.(No. 2481)

コード(Emacs)

#!/usr/bin/env scala-2.11

def palindromesWithPartition(strs:List[String]):(List[String], List[String]) = {
  strs partition (str => str == str.reverse)
}

def palindromesWithFold(strs:List[String]): (List[String], List[String]) = {
  strs.foldLeft((List[String](), List[String]()))(
    (t, str) =>
    if (str == str.reverse) (t._1 :+ str, t._2)
    else (t._1, t._2 :+ str)
  )
}

val strings: List[String] =
  List("racecar", "Scala", "abba", "C", "JavaScript", "Python", "scala")

println(palindromesWithPartition(strings))
println(palindromesWithFold(strings))

入出力結果(Terminal, REPL(Read, Eval, Print, Loop))

$ ./sample6.scala
(List(racecar, abba, C),List(Scala, JavaScript, Python, scala))
(List(racecar, abba, C),List(Scala, JavaScript, Python, scala))
$