Learning Functional Programming in Go

The shape of a functor

A functor is an algebraic type that accepts a value (or usually, a list of values) and has a map function that applies to each element in the list to produce a new functor of the same shape. What is a shape?

Let's look at an imperative example:

ints := []int{1,2,3}impInts := []int{}for _, v := range ints {   impInts = append(impInts, v + 2)}fmt.Println("imperative loop:", impInts)

Here's the output:

imperative loop: [3 4 5]

The shape in this example means a slice with three ints. We started with a slice with three ints, ran our imperative code, and ended up with a slice with three ints.

A functor gets the same results (three elements in and three elements out) but a functor does it in a different way.

We give our functor ...