Scala diff vs intersect

scala_diff_intersect.txt

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scala> import collection.immutable._
import collection.immutable._

scala> import math.Ordering._
import math.Ordering._

scala> var headers = new TreeMap[String, Any]()(Ordering.by(_.toLowerCase))
headers: scala.collection.immutable.TreeMap[String,Any] = Map()

scala> headers = headers + ("apple" -> 1) + ("potato" -> 2)
headers: scala.collection.immutable.TreeMap[String,Any] = Map(apple -> 1, potato -> 2)

scala> headers.contains("apple")
res0: Boolean = true

scala> headers.contains("APPLE")
res1: Boolean = true

scala> headers.keySet.contains("apple")
res2: Boolean = true

scala> headers.keySet.contains("APPLE")
res3: Boolean = true

scala> headers.keySet.diff(Set("banana"))
res4: scala.collection.immutable.SortedSet[String] = Set(apple, potato)

scala> headers.keySet.diff(Set("apple"))
res5: scala.collection.immutable.SortedSet[String] = TreeSet(potato)

scala> headers.keySet.diff(Set("APPLE"))
res6: scala.collection.immutable.SortedSet[String] = TreeSet(potato)

scala> headers.keySet.intersect(Set("banana"))
res7: scala.collection.immutable.SortedSet[String] = TreeSet()

scala> headers.keySet.intersect(Set("apple"))
res8: scala.collection.immutable.SortedSet[String] = TreeSet(apple)

scala> headers.keySet.intersect(Set("APPLE"))
res9: scala.collection.immutable.SortedSet[String] = TreeSet()

scala> Set("banana").intersect(headers.keySet)
res16: scala.collection.immutable.Set[String] = Set()

scala> Set("apple").intersect(headers.keySet)
res17: scala.collection.immutable.Set[String] = Set(apple)

scala> Set("APPLE").intersect(headers.keySet)
res19: scala.collection.immutable.Set[String] = Set(APPLE)