unnatural transformation

[juan_gandhi]

scala> def f(x: AnyRef) = System.identityHashCode(x)
f: (x: AnyRef)Int

scala> def s = Set("a", "bc", "def")
s: scala.collection.immutable.Set[String]

scala> val list = List(s, s)
list: List[scala.collection.immutable.Set[String]] = List(Set(a, bc, def), Set(a, bc, def))

scala> val s1 = list.map(f).toSet
s1: scala.collection.immutable.Set[Int] = Set(508760925, 1987354705)

scala> val s2 = list.toSet.map(f)
s2: scala.collection.immutable.Set[Int] = Set(508760925)

Comments

[sassa_nf]

:-)

You want

val s = Set("a", "bc", "def")

but that's a good puzzler!

[sassa_nf]

Other than that - sure, that's interaction with Java. There are other things that make identity of two equal immutable Sets observable. There is even one mutable aspect of every immutable object: the monitor used to synchronize, wait and notify. So when synchronizing, you do need to make sure the identity of the object visible to all threads is the same.

[juan_gandhi]

Oh, this is cool. Thank God I don't use threads and notify/wait anymore.