Chapter 12. Monoids
This chapter features another useful and fun type class: Monoid. This type class is for types whose values can be combined
together with a binary operation. We’ll cover exactly what monoids are and what their
laws state. Then we’ll take a look at some monoids in Haskell and how they can be of
use.
First, let’s take a look at the newtype keyword,
because we’ll be using it a lot when we delve into the wonderful world of
monoids.
Wrapping an Existing Type into a New Type
So far, you’ve learned how to make your own algebraic data types by using the
data keyword. You’ve also seen how to give
existing types synonyms with the type keyword. In
this section, we’ll look at how to make new types out of existing data types by
using the
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