# Tail recursion, fold, and more

People new to functional languages often struggle a bit with the concept of recursion, and in particular tail recursion. In this post we’ll look at both recursive and tail recursive functions using the substitution model to show their effect on the stack. We’ll also walk through deriving fold, map, and other functions from first principles because it fairly naturally follows on from this.

# Akka HTTP entity validation

Validation is something that every API developer has to deal with, but causes a surprising amount of confusion. Should the validation be done in the controller, the model, or a service class? Is the value of an attribute being invalid part of the request validation or business logic validation? By changing the way we think about validation the answers to these questions drop out, along with a nice implementation for Akka HTTP.

# Don't copy ActiveRecord

When I looked through some of Deliveroo’s non-Ruby applications, I saw that a number of them were trying to copy the ActiveRecord approach and defining data access methods on the models themselves. This is not a good approach in statically typed languages. I’ll explain why, and demonstrate the approach you should be using. It’s no secret that I’m not a fan of Go, but I’ll use it here to demonstrate as the majority of the applications I’ve seen with this problem are written in it.

# Writing a ring buffer in Scala

People coming from dynamic languages like Ruby or primitive languages like Go tend to miss the point of Scala. They tend to think in terms of mutability and often aren’t familiar with data structures beyond lists and hashes, with types and side effects being seen as fairly unimportant considerations. To try and illustrate the different way you need to think when writing Scala I’m going to write a ring buffer, as I’ve seen a few people around the office implementing them as a learning exercise.

# Go's Glass Ceiling

Go is becoming increasingly popular and I find it troubling. It’s taken me quite a while to work out why that is, and quite a few drafts to try and express it in a way that gets my point across in what I hope is a fair and balanced way. This is not a “Go is bad” post. That’s been done to death and I don’t want to rehash it. I also have no intention of denigrating people who like Go; doing so would be self-defeating given it’s them this post is really aimed at. This is a post about reaching your potential.