Scala - Core Scala - More Collections(Immutable Map)

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 7.(More Collections)、Exercises 2.(No. 3195)を解いてみる。

その他参考書籍

• Programming Scala: Scalability = Functional Programming + Objects

Exercises 2.(No. 3195)

コード(Emacs)

var directories =
  new java.io.File(".").
    listFiles.map(_.toString.replace("./", "")).
    filter(_.head != '.')

val letters = collection.mutable.Map[Char,Int]()

for (directory <- directories) {
  val ch:Char = directory.head
  if (letters.contains(ch)) {
    letters(ch) += 1
  } else {
    letters(ch) = 1
  }
}

println(letters)

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

$ scala-2.11 sample3.scala
Map(s -> 12, d -> 7, o -> 2)
$