Learning Functional Programming in Go

Identity operation

Identity law of our category says the identity morphism of A is A.

Every object has a morphism pointing back to itself.

When we have more than one object, we denote which ID we're talking about with a subscript, for example, idA.

This graph says f o idA  = f.

In other words, the morphism of f after idA is the same as the morphism of f. Here's a concrete example:

The identity morphism for the natural number 3 is a function ...