Learning Functional Programming in Go

A Category

A category is defined by its objects and the arrows that connect the objects and all compositions.

For every two arrows (f and g), we must define their composition (g o f).

The elements/data of a category theory include:

• Categories/sets: is a grouping of objects
• Objects: dots/points/a primitive with no properties no structure
• Morphisms: (arrows) something that goes between two objects/elements

We write objects with upper case letters (such as A, B, C, and so on). We write arrows in lower case letters (such as f, g, h, and so on).

Arrows have a beginning and an end. Objects in the beginning of the arrow are in the domain; arrows at the end arrows are in the range (also known as codomain).