Question

Let’s say I have function:

def foo[A,B](a : A, f : A => B) = ... 

And I call it:

var x = new X()
foo(x, obj => ...

At this point it is clear that type of argument of lambda (obj here) is X (C# works that way for example).

However in Scala I have to write:

foo(x, (obj : X) => ...

It causes a lot of noise in code.

Question

How to write my function foo to avoid such over-specification on every call? Or maybe I am missing something and adding type is needed because such call (without type info) would be ambiguous.

Answer 1

I think currying in general is the way to go, but if you have lots of functions with the same type of argument you could do something like this:

class Foo[T] {
  def apply[R](x: T, f: T => R) = f(x)
}

val foo = new Foo[Int]

foo(10, x => "Result: " + x.toString) // String = Result: 10
foo(10, x => x.toString * 5)          // String = 1010101010
foo(42, x => x + 100)                 // Int = 142
foo(12, x => Seq.iterate(x, 5)(_*2))  // Seq[Int] = List(12, 24, 48, 96, 192)