Scala - Core Scala - First-Class Functions(Invoking Higher-Order Functions)

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

開発環境

• OS X Yosemite - 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 5.(First-Class Functions)、Exercises 6.(No. 1874)を解いてみる。

その他参考書籍

• Programming Scala: Scalability = Functional Programming + Objects

Exercises 6.(No. 1874)

コード(Emacs)

def conditional[T](x:T, p:T => Boolean, f: T => T):T = {
  if (p(x))
    f(x)
  else
    x
}

def p1[T](x:T): Boolean = true
def p2[T](x:T): Boolean = false
def f1[T](x:T): String = "Hello, World!"
def f2[T](x:T): String = "Hello, Scala!"

val x = 10

println(conditional(x, p1, f1))
println(conditional(x, p1, f2))
println(conditional(x, p2, f1))
println(conditional(x, p2, f2))

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

$ scala-2.11 sample6.scala
Hello, World!
Hello, Scala!
10
10
$