Scalaでも>>とか<<で関数合成できるように。

ComposableFunction1.scala

scala> trait ComposableFunction1[-T1, +R]  {
     |   val f: T1 => R
     |   def >>[A](g:R => A):T1 => A = f andThen g
     |   def <<[A](g:A => T1):A => R = f compose g
     | }
defined trait ComposableFunction1

scala> implicit def toComposableFunction1[T1,R](func:T1 => R) = new ComposableFunction1[T1,R]{ val f = func }
toComposableFunction1: [T1,R](func: (T1) => R)java.lang.Object with ComposableFunction1[T1,R]

scala> 

scala> val plus2  = (it:Int) => { it + 2 }
plus2: (Int) => Int = <function1>

scala> val times3 = (it:Int) => { it * 3 }
times3: (Int) => Int = <function1>

scala> val times3plus2 = plus2 << times3
times3plus2: (Int) => Int = <function1>

scala> times3plus2(3) 
res0: Int = 11

scala> val plus2times3 = times3 << plus2
plus2times3: (Int) => Int = <function1>

scala> plus2times3(3) 
res1: Int = 15

scala> (times3 >> plus2)(3)
res2: Int = 11