Monoid examples

We'll cover three types of monoid here:

• Name monoid
• Int slice monoid
• Line item monoid

That's right. We're going to turn that invoice into a monoid!

Name monoid

Let's see what we can do with a name. First, we define an interface that has two methods, Append and Zero. We wrap our name in nameContainer.

Our nameContainer is a struct with a single string field, name. Our Append method appends the given name to the long name string it's building up that lives in the magical nameContainer. Our zero morphism for our name string is an empty string.

The content of src/monoid/name_monoid.go would look as follows:

package monoid

type NameMonoid interface {
   Append(s string) NameMonoid
   Zero...