Scala Seq comparison

Question

is there a way in Scala to compare two sequences in a way that it returns true if it contains the same elements, regardless of order and repetitions?

Seq("1", "2") vs Seq("2", "1")           => true
Seq("3", "1", "2") vs Seq("2", "1", "3") => true
Seq("1", "1", "2") vs Seq("2", "1")      => true

Thanks

ps this is not a duplicated of this because it also asks to exclude duplicated from the check and it is using SEQ instead of LIST.

Possible duplicate of [Is there an API method that compares contents of a Seq irrespective of order?](http://stackoverflow.com/questions/3622895/is-there-an-api-method-that-compares-contents-of-a-seq-irrespective-of-order) — THIS USER NEEDS HELP, Jan 03 '17 at 18:55

score 13 · Accepted Answer · answered Jan 08 '16 at 19:39

13

Convert to sets and compare those

answered Jan 08 '16 at 19:39

Jens Schauder

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why this answer has been down voted? it seems to work fine – ab_732 Jan 08 '16 at 19:51
when converted to sets Seq("1", "1", "2").toSet will be equal to Seq("1","2").toSet because of same elements – stanislav.chetvertkov Jan 08 '16 at 20:06
5

@stanislav.chetvertkov Which in this question seems desired. – Suma Jan 08 '16 at 20:12

score 0 · Answer 2 · answered Jan 08 '16 at 23:31

@ def sameElements[A](a: Seq[A], b: Seq[A]) = a.toSet == b.toSet
defined function sameElements
@ sameElements(Seq("1", "2"),Seq("2", "1"))
res2: Boolean = true
@ sameElements(Seq("3", "1", "2"),Seq("2", "1", "3"))
res3: Boolean = true
@ sameElements(Seq("1", "1", "2"),Seq("2", "1"))
res4: Boolean = true

stanislav.chetvertkov · Answer 3 · 2016-01-09T12:04:13.603

-1

Introduce an extension object with === operator. It will be used implicitly for the same typed Seqs

implicit class SeqOps[A](it:Seq[A]){
  def === (that:Seq[A]) = it.toSet == that.toSet
}

import Test.SeqOps

Seq("1", "2") === Seq("2", "1") shouldBe true

edited Jan 09 '16 at 12:04

answered Jan 08 '16 at 19:46

stanislav.chetvertkov

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score -3 · Answer 4 · answered Jan 08 '16 at 19:52

-3

You just need to turn the sequences to sets:

val n1: Seq[Int] = Seq(1, 3, 4)
    val n2: Seq[Int] = Seq(3, 4, 1)

    if(n1.toSet.equals(n2.toSet)){
      println("The sequences have the same elements.")
    }

answered Jan 08 '16 at 19:52

farohetch13

1
1

Scala uses == for checking objects structural equality – stanislav.chetvertkov Jan 08 '16 at 20:14
link to difference between == and equals (http://stackoverflow.com/questions/7681161/whats-the-difference-between-and-equals-in-scala) – farohetch13 Jan 08 '16 at 20:25
@farohetch13 Your own link seems to suggest that `==` is a better method compared to `equals`? `==` seems to wrap around `equals` but handles null better – THIS USER NEEDS HELP Jan 03 '17 at 18:54

Scala Seq comparison

4 Answers4