Implementing ifTrue, ifFalse, ifSome, ifNone, etc. in Scala to avoid if(…) and simple pattern matching

Question

In Scala, I have progressively lost my Java/C habit of thinking in a control-flow oriented way, and got used to go ahead and get the object I\'m interested in first, and the

Answer 1

You may be looking at the problem too specifically. You would probably be better off with the pipe operator:

class Piping[A](a: A) { def |>[B](f: A => B) = f(a) }
implicit def pipe_everything[A](a: A) = new Piping(a)

Now you can

("fish".length > 5) |> (if (_) println("Hi") else println("Ho"))

which, admittedly, is not quite as elegant as what you're trying to achieve, but it has the great advantage of being amazingly versatile--any time you want to put an argument first (not just with booleans), you can use it.

Also, you already can use options the way you want:

Option("fish").filter(_.length > 5).
  map (_ => println("Hi")).
  getOrElse(println("Ho"))

Just because these things could take a return value doesn't mean you have to avoid them. It does take a little getting used to the syntax; this may be a valid reason to create your own implicits. But the core functionality is there. (If you do create your own, consider fold[B](f: A => B)(g: => B) instead; once you're used to it the lack of the intervening keyword is actually rather nice.)

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Edit: Although the |> notation for pipe is somewhat standard, I actually prefer use as the method name, because then def reuse[B,C](f: A => B)(g: (A,B) => C) = g(a,f(a)) seems more natural.