What is the basic collection type in Scala?

Question

Or in other words what is the equivalent of C# IEnumerable<T> in Scala? I thought it is Seq[T], but I already found out, that HashMap does not implement this, so it cannot be true.

So, what is it?

Answer 1

Traversable and Iterable are base traits for scala collections. Actually, Iterable extends Traversable.

From scala api doc for Iterable:

A base trait for iterable collections.

This is a base trait for all Scala collections that define an iterator method to step through one-by-one the collection's elements.

And Traversable:

This is a base trait of all kinds of Scala collections. It implements the behavior common to all collections, in terms of a method foreach.

Here is a nice pics from scala-lang site that represents scala collections hierarchy (mutable and immutable respectively):

Immutable: