Professional Scala

Abstracting on Sequences

All Scala collections descend from a common trait called Traversable. The design adopted for Scala collections allows one to use higher-order functions similarly in nearly all collections, with proper return types in specific instances. Treating collections as sequences, or as containers of elements, allows one to use different data structures seamlessly.

The Traversable Trait

At the root of the collections hierarchy is the Traversable trait. The Traversable trait has a single abstract method:

def foreach[U](f: Elem => U)

The implementation of this method is sufficient for the Traversable trait to provide a series of useful higher-order methods.

We would like to focus on the map operations. The map method takes a function ...