What is 関数型言語? ref: http://qiita.com/items/9f0b9cc5c0f28deb48e2

file0.txt

y = sin(x)

file10.txt

$ scala NoneSideEffect.scala
add=6
add=6
add=6

file12.txt

$ scala SideEffect.scala
add=6
add=7
add=6

file13.txt

def add(x:Int, y: Int) = x + y

file14.txt

var add = (x:Int, y:Int) => x + y

file2.txt

$ scala FunctionExample.scala
y=6
y=7

file4.txt

$ scala Mutable.scala
Mutable
Change mutable

file6.txt

$ scala Immutable.scala
Immutable.scala:6: error: reassignment to val
immutable = "Change immutable"
          ^
one error found

file8.txt

$ scala SideEffect.scala
total=1
total=2
total=3

FirstClassFunction.scala

object FirstClassFunction{
  def main(args: Array[String]){
    val add = (x: Int) => {
      val _add = (y: Int) =>  y + 5
      _add(x)
    }

    printf("add=%s \n", add(1))
    printf("add=%s \n", add(2))
    printf("add=%s \n", add(1))
  }
}

FunctionExample.scala

object FunctionExample{
  def main(args: Array[String]){

    var calculate = (x: Int) => x + 5 : Int

    printf("y=%s \n", calculate(1))
    printf("y=%s \n", calculate(2))
  }
}

Immutable.scala

object Immutable{
  def main(args: Array[String]){
    val immutable = "Immutable"
    printf("%s ", immutable)

    immutable = "Change immutable"
    printf("%s ", immutable)
  }
}

Mutable.scala

object Mutable{
  def main(args: Array[String]){
    var mutable = "Mutable"
    printf("%s ", mutable)

    mutable = "Change mutable"
    printf("%s ", mutable)
  }
}

NoneSideEffect.scala

object NoneSideEffect{
  def main(args: Array[String]){
    var add = (x: Int) => x + 5

    printf("add=%s \n", add(1))
    printf("add=%s \n", add(1))
    printf("add=%s \n", add(1))
  }
}

SideEffect.scala

object SideEffect{
  var total = 0

  def main(args: Array[String]){
    var add = (x:Int) => {
      total+=x
      total
    }

    printf("total=%s \n", add(1))
    printf("total=%s \n", add(1))
    printf("total=%s \n", add(1))
  }
}