Why can traits in scala.collection create an instance? -

Why can traits in scala.collection create an instance? -

i trying next code in scala, coming an overview of collections api.

import collection._ scala> traversable(1, 2, 3) res5: traversable[int] = list(1, 2, 3) scala> iterable("x", "y", "z") res6: iterable[string] = list(x, y, z) scala> map("x" -> 24, "y" -> 25, "z" -> 26) res7: scala.collection.map[string,int] = map(x -> 24, y -> 25, z -> 26) scala> sortedset("hello", "world") res9: scala.collection.sortedset[string] = treeset(hello, world) scala> indexedseq(1.0, 2.0) res11: indexedseq[double] = vector(1.0, 2.0)

the result shows trait can phone call apply method create instance of implementation. after looking scala.collection.package object, found nothing. think there must somewhere binds trait subclass , imports program. can explain is?

you're calling apply on trait's companion object, not on trait.

for example, traversable:

the trait

the object

if click on apply in companion object's scaladoc, can see traversable object inherits apply method genericcompanion, has link source can see how it's implemented.

scala collections