How to write the function isFunction in scala?

Question

How can i write a isFunction function in scala, so that this works:

def isFunction(x:Any) = /* SomeCode */

println(isFunction(isFunction _)) //true
println(isFu         


        

Answer 1

I am not a special fan of your solution and I agree with Daniel Sobral comment. If I had to implement it I would do that in a type safe way, through implicit conversion

trait IsFunctionable {
  def isFunction : Boolean
}

object IsFunctionable {

  object IsFunction extends IsFunctionable {
    def isFunction = true
  }

  object IsNotFunction extends IsFunctionable {
    def isFunction = false
  }

  implicit def function0ToIsFunctionable[A<:Function0[_]](a:A):IsFunctionable = IsFunction
  implicit def function1ToIsFunctionable[A<:Function1[_,_]](a:A):IsFunctionable = IsFunction
  implicit def function2ToIsFunctionable[A<:Function2[_,_,_]](a:A):IsFunctionable = IsFunction
  // and so on

  implicit def anyToIsFunctionable[A](a:A):IsFunctionable = IsNotFunction
}

And now you can happily test in the repl:

scala>  import IsFunctionable._
import IsFunctionable._

scala>  val a: Int => Int = _ * 2
a: Int => Int = 

scala>  val b: (Int,Int) => Int = (_*_)
b: (Int, Int) => Int = 

scala>  a(3)
res0: Int = 6
scala>  b(2,4)
res3: Int = 8

scala>  a.isFunction
res4: Boolean = true

scala>  b.isFunction
res5: Boolean = true

scala>  "Hello".isFunction
res6: Boolean = false