Better Know Enumerable: IntroductionSep 17, 2014 • Brian Cobb
Enumerable module is the backbone that gives
IO, and a handful of other core classes methods like
More than basic traversal and sorting, it enables a mental and practical shift from imperative to functional programming.
For instance, we could use
each and a few conditionals to figure out which top-level classes include
However, using the
select methods provided by
Enumerable break down the problem in a more direct way and without local mutable state.
An in-depth exploration of the rest of
Enumerable could fill a small book, and this post will not attempt to fill in all the gaps.
Instead, it provides a few examples using common and uncommon parts of
Enumerable’s interface, and hopefully motivates further experimentation with the rest of the module.
Despite being used in the proverbially grainy and greyscale example above,
each is the linchpin of
In order for a class to include
Enumerable it must implement
SentenceSearch below will traverse through all sentences which contain some
word in a given
body (for a naïve definition of “sentence”).
We’ll use it to find the word “pudding” in an excerpt from Dickens’ Great Expectations (text copied from Project Gutenberg).
Being able to traverse through these sentences is useful—many search engines provide this sort of view when displaying search results—but
Enumerable facilitates working with these collections of sentences in a surprising number of ways.
We can find the shortest and longest sentence:
Or just the shortest sentence:
Using the union operation on
|, we can compile the collection of unique words in all of the sentences:
Enumerable is a generic module for collection traversal; with a little imagination we could conjure up dozens of additional ways to process the base collection of pudding-related sentences.
In future posts, I’ll cover
Enumerable’s methods in greater depth, and show real-world examples of refactoring towards an
Enumerable class to reap the benefits of its familiar and powerful interface.