Portable Tech Team Deep Dive - fp-ts Deep Dive

A small project that helps illustrate some of the key features of the fp-ts library as an introduction to functional programming.

Introduction

We'll be looking at some of the challenges that we'd face if we were to adopt some of the key aspects of modern functional programming.

• no instances
• no mutable state

Some of the other things to consider later on might be how to:

• perform and represent effects
• create abstractions that allow for the equivalent of dependency injection in the OO paradigm

Agenda

• Getting started
• Quick refresher on Typescript
• Let's look at our object oriented application
• How do we solve some of these things in the functional application

Getting Started

You will need NodeJS and Yarn installed on your machine.

Once you have that, to install all dependencies, run yarn.

Running yarn start will run the application.

Documentation pages of interest: https://www.typescriptlang.org/docs/handbook/unions-and-intersections.html#discriminating-unions https://www.typescriptlang.org/docs/handbook/generics.html

Quick refresher on Typescript

You may want to take a look at the Data Modelling Deep Dive in Typescript for some exercises to get up to speed for this session.

However, at a high level - we want to be able to understand the following Typescript types.

• Option
• Either<A,B>

Option Type

Option is a type that represents two states:

either there is a value; or there isn't An example of this would be Option - if a value has this type, there will either be a string available or there will be nothing.

Also note that Option is a generic type, allowing you to specify any particular concrete type for .

Either Type

Either<A,B> is a type that represents two states:

either there a value of one type; or there is a value of a different type; An example of this would be Either<string, number> - if a value has this type, there will either be a string available or there will be a number.

This type is commonly used to represent a result of a function call, that might fail. eg. you either get a success with the result, or you get a failure with the error information.

Let's look at our object oriented application

TODO

How do we solve some of these things in the functional application

TODO