Question

I have a function foo that accepts a Boolean function

def foo( f:(_)=>Boolean ) = //do something with f

I can call foo as follows

foo( (x:Int) => x == 0 )

Now, I want modify foo to accept any function that returns Boolean. eg. the modified foo should work for the following cases.

foo( (x:Int, y:Int) => x == y)
foo( (x:Int, y:Int, z:Int) => x == y && y == z)
foo( (x:Double, y:Double, z:Double, p:Double) => x < y && y < z && z < p)
//and so on...

My first attempt was to modify foo as follows

def foo2( f:(_*)=>Boolean ) = //do something with f

But this does not work.

Answer 1

What @Nicolas said.

You can make the call site code slightly nicer using Function.tupled.

scala> def foo[A](f: A => Boolean) = 0
foo: [A](f: A => Boolean)Int

scala> import Function.tupled
import Function.tupled

scala> foo(tupled((x: Int, y: Int) => x == y))
res0: Int = 0

scala> foo(tupled((x: Int, y: Int, z: Int) => x < y && y < z))
res1: Int = 0