CODEWITHSUNDEEP
xtend
wheeler
wheeler

Reputation: 3251

Combining Sets in xtend

I have two sets:

val Set<Integer> setA = #{1, 2, 3}
val Set<Integer> setB = #{3, 4, 5} + setA

I would expect setB to contain 1, 2, 3, 4, 5.

However, the + operator returns an instance of Iterable, instead of a Set.

Are there any xtend shortcuts that would allow me to do what I want?

Upvotes: 2

Views: 329

Answers (2)

kapex
kapex

Reputation: 29969

Without redefining operators, you have to convert the Iterable to a Set manually.

val Set<Integer> setA = #{1, 2, 3}
val Set<Integer> setB = (#{3, 4, 5} + setA).toSet

If you have a mutable set, there is one other way: The += operator, which is a shortcut for addAll on any collection.

val Set<Integer> setA = #{1, 2, 3}
val Set<Integer> setB = newHashSet(3, 4, 5)
setB += setA

Neither solution look particularly nice and you probably want to avoid mutability.

As suggested in the other answer, Guava's Sets.union method might come in handy, though I would rather import it as static extension than redefining operators. Then you can use:

val Set<Integer> setA = #{1, 2, 3}
val Set<Integer> setB = #{3, 4, 5}.union(setA)

Be careful though, union returns a view of both sets, which can change if the underlying sets are mutable.

Upvotes: 0

Sebastian Zarnekow
Sebastian Zarnekow

Reputation: 6729

I'm afraid there is no backed in support for a union. You may want to add an operator_plus for two sets and delegate to Guavas Sets.union.

def <T> Set<? extends T> operator_plus(Set<? extends T> left, Set<? extends T> right) {
  return Sets.union(left, right)
}

Upvotes: 2

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