Vavr: Proposal: Scala's "wunderbar" for functions

[wernerdegroot]

Scala has the "wunderbar" which will let you apply a couple of arguments to a function while leaving others open.

The following would create a function that takes a single argument (the one we're "leaving open" with _):

addThree(1, _, 3)

We could implement something similar in Vavr by introducing a Placeholder class

public final class Placeholder {

  public static Placeholder __ = new Placeholder();

  private Placeholder() {
  }
}

We could then come up with a whole bunch of apply-overloads, like the following for Function3:

 default Function1<T2, R> apply(T1 first, Placeholder secondPlaceholder, T3 third) {
  return (second) -> apply(first, second, third);
 }

To be able to do the following in Vavr:

addThree.apply(1, __, 3)

This would require 2^args number of overloads (up until 256 for Function8). I've already written a simple script to generate all these overloads.

Would do you think?

[danieldietrich]

Thanks for your suggestion! Unfortunately that is no option for us. My current strategy is to reduce the number of generated types in Vavr. Once we had a function and tuple arity of 26. That would be 2^26 overloads. Opening the Javadoc would blow up the browser. 😱

What is wrong with creating the function the direct way in places where you need it?

(n) -> addThree.apply(1, n, 3)

I will close this issue but the discussion is still open on any questions!