Jack Marchant

Principal Software Engineer @ Deputy

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First Impressions of Elixir

Elixir is a functional programming language based on Erlang. I’m told it’s very similar to Ruby, with a few tweaks and improvements to the developer experience and language syntax.

[Detour – buckle your seatbelts]

I’m drawn to Elixir because of my interest in Functional Programming, generally and specially in JavaScript. I started by learning techniques to make pure functions so that I could more easily test my code. Then, I progressed into learning about composition, currying and partial application in JavaScript, particularly as it was useful to know when using Redux.

[take a breather, that’s a lot of buzz]

[enough breathing]

So, then (without mastering any of the above) I decided to try my luck with learning functional programming theory (which is basically just math). That was fun too.

I have twisted and turned through it all, trying to figure out what FP means, and to be honest I’m enjoying it – so why not try to pick up a language that is purely (get it?) functional.

[back to Elixir…/Detour]

Now you know why I’m interested in learning a functional programming language such as Elixir, let’s go on a mythical journey together to see what I’ve learned.

Learning new things is hard

One of the best things I’ve noticed about Elixir – given at this point in time I’ve used it for about a week – is that it’s incredibly focussed on developer experience.

I think the creator of Elixir (José Valim) must have looked at Erlang and thought we could do better than this. The best people take great ideas and make them easier for other people to learn.

Here’s a few things Elixir does or helps you do as a developer (in list format because who doesn’t like a good list?)

That’s plenty of things. What more do you want?

All of this makes it easier for a willing developer to pick up Elixir and give it a go. Nobody wants to be fiddling around with their development environment in a shameful attempt to start learning a new language.

FP is FP

Functional programming is fucking powerful. It shouldn’t be underestimated. I don’t want to spend any more than 3 seconds walking through my code (and dissecting my brain that day) because I wasn’t bothered to create a function with a clear interface and signature. I am starting to think a function with more than say, 10 lines, is too long and doing too much.

It’s easy to say Elixir is better because it enforces strict rules about what and how you should write your code but I think it would still be possible to write shitty code in any language, just easier in others.

Given that Elixir is an FP language it makes sense that all of the Elixir modules follow its general principles. Taking my early experiences with Elixir into account, I can say I appreciate the strict-ness of the language coming from JavaScript, but there’s also something to be said about the creativity and expressiveness you can have writing functional JavaScript – and there’s plenty of people talking about that now.

It’s interesting that I haven’t seen more people checking out Functional languages after discovering the power of it in JavaScript. Maybe they just haven’t written a kickass article about it?

WTF? (What the feature?!)

In keeping with Elixir’s functional ties, there’s a feature called Pattern Matching, which I’m very excited to learn more about. I don’t think this is an Elixir-only feature but it’s certainly the first time I have come across it.

The idea (from what I can gather) is that you can define a function as a copy of another function with values in place of parameters and when the value is equal to what is passed in, it will run that function, instead of another further down.

As an example, I had a recursive function that takes a list, but I only want it to run when there are items in the list (otherwise it would get stuck in a recursive loop).

My instinct would have been to use an if statement to check whether there are items and return early – but with Pattern Matching you can say when the first parameter is an empty list, just return early. You have to make sure the pattern matching function is defined before any function you want to override.

This concept separates the two cases into two functions, rather than having one function that handles all cases. As a beginner that is a difficult thing to realise but I’m interested to see whether it improves code readability.

Where do we go ? (Where do we go now)

Functional programming has been around for ages, but as software engineering on the web matures, developers begin to question how we’ve done things and look for something better.

Elixir sounds like a new challenge to me and has some good things going for it. Now seems like the perfect time for me to pick it up so my goal will be to become more comfortable with it and be able to start a project from scratch and build something myself without a tutorial helping me along.


So far

If you’ve read this far, I congratulate you on your job well done. Take the rest of the day off.

Here are some links to Elixir work I’ve done so far:

. . .

how does a relational database index really work

A common question in software engineering interviews is how can you speed up a slow query? In this post I want to explain one answer to this question, which is: to add an index to the table the query is performed on.

refactoring for performance

I spend most of my time thinking about performance improvements. Refactoring is tricky work, even more so when you’re unfamiliar with the feature or part of the codebase.

exploring async php

Asynchronous programming is a foundational building block for scaling web applications due to the increasing need to do more in each web request. A typical example of this is sending an email as part of a request.

maintaining feature flags in a product engineering team

I have mixed feelings about feature flags. They are part of the product development workflow and you would be hard pressed to find a product engineering team that doesn’t use them. Gone are the days of either shipping and hoping the code will work first time or testing the life out of a feature so much that it delays the project.

technical interviewing

When I first started interviewing candidates for engineering roles, I was very nervous. The process can be quite daunting as both an interviewer and interviewee. The goal for the interviewer is to assess the candidate for their technical capabilities and make a judgement on whether you think they should move to the next round (there’s always a next round). Making a judgement on someone after an hour, sometimes a bit longer, is hard and error prone.

using a dependency injection container to decouple code

Dependency Injection is the method of passing objects to another (usually during instantiation) to invert the dependency created when you use an object. A Container is often used as a collection of the objects used in your system, to achieve separation between usage and instantiation.

3 tips to help with working from home

Working from home has been thrust upon those lucky enough to still have a job. Many aren’t sure how to cope, some are trying to find ways to help them through the day. Make no mistake, this is not a normal remote working environment we find ourselves in, but nonetheless we should find ways to embrace it.

making software a three step process

One of the most useful tips that has guided much of my decision over the years has been this simple principle: three steps, executed in sequential order;

help me help you code review

Code Reviews are one of the easiest ways to help your team-mates. There are a number of benefits for both the reviewer and pull request author:

a pratical guide to test driven development

It’s been a while since I last wrote about why testing is important, but in this post I thought I would expand on that and talk about why not only unit testing is important, but how a full spectrum of automated tests can improve productivity, increase confidence pushing code and help keep users happy.

facade pattern

Design Patterns allow you to create abstractions that decouple sections of a codebase with the purpose of making a change to the code later a much easier process.

the problem with elixir umbrella apps

Umbrella apps are big projects that contain multiple mix projects. Using umbrella apps feels more like getting poked in the eye from an actual umbrella.

broken windows

Ever get the feeling that adding this "one little hack", a couple of lines of code, won't have much of an impact on the rest of the codebase? You think nothing of it and add it, convincing your team members it was the correct decision to get this new feature over the line. In theory, and generally speaking, I would kind of agree with doing it, but every hack is different so it's hard to paint them all with the same brush. If you've been doing software development for long enough you can see this kind of code coming from a mile away. It's the kind of code that can haunt your dreams if you're not careful.

lonestar elixir 2019

Last week was Lonestar ElixirConf 2019 held in Austin, Texas. The conference ran over 2 days and was the first Elixir conference I had been to.

genserver async concurrent tasks

In most cases I have found inter-process communication to be an unnecessary overhead for the work I have been doing. Although Elixir is known for this (along with Erlang), it really depends on what you’re trying to achieve and processes shouldn’t be spawned just for the fun of it. I have recently come across a scenario where I thought having a separate process be responsible for performing concurrent and asynchronous jobs would be the best way to approach the problem. In this article I will explain the problem and the solution.

best practices third party integrations

When we think about what an application does, it's typical to think of how it behaves in context of its dependencies. For example, we could say a ficticious application sync's data with a third-party CRM.

you might not need a genserver

When you're browsing your way through Elixir documentation or reading blog posts (like this one), there's no doubt you'll come across a GenServer. It is perhaps one of the most overused modules in the Elixir standard library, simply because it's a good teaching tool for abstractions around processes. It can be confusing though, to know when to reach for your friendly, neighbourhood GenServer.

offset cursor pagination

Typically in an application with a database, you might have more records than you can fit on a page or in a single result set from a query. When you or your users want to retrieve the next page of results, two common options for paginating data include:


Protocols are a way to implement polymorphism in Elixir. We can use it to apply a function to multiple object types or structured data types, which are specific to the object itself. There are two steps; defining a protocol in the form of function(s), and one or many implementations for that protocol.


Recently, I've been writing a tonne of Elixir code, some Phoenix websites and a few other small Elixir applications. One thing that was bugging me every time I would create a new project is that I would want to add Docker to it either straight away because I knew there would be a dependency on Redis or Postgres etc, or halfway through a project and it would really slow down the speed at which I could hack something together.

working with tasks

While writing Understanding Concurrency in Elixir I started to grasp processes more than I have before. Working with them more closely has strengthened the concepts in my own mind.

understanding concurrency

Concurrency in Elixir is a big selling point for the language, but what does it really mean for the code that we write in Elixir? It all comes down to Processes. Thanks to the Erlang Virtual Machine, upon which Elixir is built, we can create process threads that aren't actual processes on your machine, but in the Erlang VM. This means that in an Elixir application we can create thousands of Erlang processes without the application skipping a beat.

composing ecto queries

Ecto is an Elixir library, which allows you to define schemas that map to database tables. It's a super light weight ORM, (Object-Relational Mapper) that allows you to define structs to represent data.

streaming datasets

We often think about Streaming as being the way we watch multimedia content such as video/audio. We press play and the content is bufferred and starts sending data over the wire. The client receiving the data will handle those packets and show the content, while at the same time requesting more data. Streaming has allowed us to consume large media content types such as tv shows or movies over the internet.

elixir queues

A Queue is a collection data structure, which uses the FIFO (First In, First Out) method. This means that when you add items to a queue, often called enqueuing, the item takes its place at the end of the queue. When you dequeue an item, we remove the item from the front of the queue.

composing plugs

Elixir is a functional language, so it’s no surprise that one of the main building blocks of the request-response cycle is the humble Plug. A Plug will take connection struct (see Plug.Conn) and return a new struct of the same type. It is this concept that allows you to join multiple plugs together, each with their own transformation on a Conn struct.

elixir supervision trees

A Supervision Tree in Elixir has quite a number of parallels to how developers using React think about a component tree. In this article I will attempt to describe parallel concepts between the two - and if you've used React and are interested in functional programming, it might prompt you to take a look at Elixir.

surviving tech debt

Technical debt is a potentially crippling disease that can take over your codebase without much warning. One day, you’re building features, the next, you struggle to untangle the mess you (or maybe your team) has created.

pattern matching elixir

Before being introduced to Elixir, a functional programming language built on top of Erlang, I had no idea what pattern matching was. Hopefully, by the end of this article you will have at least a rudimentary understanding of how awesome it is.

first impressions elixir

Elixir is a functional programming language based on Erlang. I’m told it’s very similar to Ruby, with a few tweaks and improvements to the developer experience and language syntax.

write unit tests

Unit testing can sometimes be a tricky subject no matter what language you’re writing in. There’s a few reasons for this: