CODEWITHSUNDEEP
scalacollections
Martin Flower
Martin Flower

Reputation: 371

Scala - compare two Option[Seq[String]]

I am new to the Scala language - I seem to have a problem finding the right syntax for sorting and comparing two Option[Seq[String]]. The two should be equals irrespective of contents order. The last line in this test fails. I hope this code sufficiently documents the question.

  package seqtest

import org.scalatest.{Matchers, FlatSpec}

class SortCollectionsTest extends FlatSpec with Matchers {

  "Different seq order" should "not affect equality" in {

    val seqAB1 = Seq("A","B")
    val seqAB2 = Seq("A","B")
    // two different sequences are equal
    assert(seqAB1 == seqAB2)

    val seqBA1 = Seq("B","A")
    // two different sequences are not equal if different order
    assert(seqAB1 != seqBA1)

    // but is possible to convert sequence to list and sort
    assert(seqAB1.toList.sorted == seqBA1.toList.sorted)


    // now do the same thing with Option

    val someSeqAB1 = Some(Seq("A","B"))
    val someSeqAB2 = Some(Seq("A","B"))
    // two different option sequences are equal
    assert(someSeqAB1 == someSeqAB2)

    val someSeqBA = Some(Seq("B","A"))
    // two different optional sequences are not equal if different order
    assert(someSeqAB1 != someSeqBA)

    // Option can be converted into list (unsorted)
    assert(someSeqAB1.toList != someSeqBA.toList)

    // problem
    // two different optional sequences cannot be sorted
    // compilation error
    // Error:(42, 30) No implicit Ordering defined for Seq[String].
    // Error:(42, 30) not enough arguments for method sorted: (implicit ord: scala.math.Ordering[Seq[String]])List[Seq[String]].
    // Unspecified value parameter ord.
    assert(someSeqAB1.toList.sorted == someSeqBA.toList.sorted)
  }
}

Upvotes: 2

Views: 2467

Answers (2)

Sergey
Sergey

Reputation: 2900

Since you're using Matchers i'd suggest to do something like this:

someSeqAB1 should not be empty
someSeqBA should not be empty
someSeqAB1.get should contain theSameElementsAs someSeqBA.get

Upvotes: 1

pedrofurla
pedrofurla

Reputation: 12783

I think the much easier solution would be to map the options:

assert(someSeqAB1.map{ _.sorted } == someSeqBA.map{ _.sorted })

Btw, to the sorted version the assertion is equal.

Upvotes: 2

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