Decomposition through exposition towards eventual composition

Why FP

Simple to reason about
- inputs yield outputs
- data and behavior are the same
Simple to decompose
- functions are truly first class
- when everything is composed of functions/data powerful patterns of abstraction become available
- currying
Simple to compose
- partial application | a function without all it’s arguments simply returns a function expecting those additional args
- (implicit in ML style languages, explicit in lisps/clojure)
Composition leads to reuse
- Almost anything you can imagine writing that’s a general operation, you will almost certainly see that it was available to you before hand.
- Learn to recognize patterns and be tickled by them, intuit that someone smarter than you has probably solved this.
Programming, motherfucker
- it matters
- …the more you know!
- exposure and experimentation build & refine tastes
- Do you have an argument for not knowing more? Is putting the shoe on the other foot a bad idea sometimes?

Why Clojure

Lightweight Syntax
- very little to learn, data and behavior share representation
- omg parens. Whatever, like everything about programming you currently understand made sense to you immediately.
- I can’t read arabic, so it’s fucking worthless?
Pragmatic
- Nearing two years old, it’s not just going to go away
- first class citizen of the JVM. There is a Java library for your problem, and it’s probably a lot more refined than you realize.
- ie: ruby has can reach out to C, but there’s almost no reason you would unless you really had to. It’s hard.
- performant… without the expense of obfuscation. Write code as succinct (if not more so), than your current code, and watch it fly
- people are using it on real projects to solve real problems
- Relevance
- 8th light
- Edgecase
- Atomic Object
- … and plenty of startups
- … and plenty of enterprise companies
Hype
- founded hype, at that. Solves real problems, unlike things such as Node.js (if evented concurrency was a good idea, tornado or eventmachine would be successful)
- a real chance to innovate and be thought leaders
- making a grand impact on the Ruby and Rails community is really hard right now.
- … but maybe if we listened to other communities more we could see what we’re lacking
- it’s a two-way street
Fun
- A lot of what attracted me to the Ruby community when I came into is present in the Clojure community
- Want to work with passionate and intelligent people?
  - Attract talent! Recruiting is HARD, especially right now
  - it’s just compounded with super smart JVM/Java guys
  - and super smart Lisp guys
  - and super smart CS guys
- and you don’t need to rewrite every tool ever. The ecosystem is already there.
- when you do need to rewrite a tool, guess what, you’re a hero. Well done.
- palpable excitement from the community. Haven’t felt that in a while here :(
Simplicity vs Ease
- Ruby is easy… sort of
- Clojure is hard(er)… sort of
- Ruby makes it really easy to get a reasonably tiny system up and running quickly, and achieve sorcery in the process
- Clojure (and FP in general) make it really easy to get reasonably large systems up and maintainable, and achieve wizardry
- A LOT of our apps go longer than 3-4 months. Perhaps we should think about things longer term.

OOP vs FP

This is a stupid slide, we can talk about it later.

Making it Real

Service Layer behind a Rails app
- we should probably be designing a lot more of our applications this way anyway
Full Stack
- the framework support isn’t quite there yet for getting up and running quickly
- …but most of our projects last longer than a month anyway
- and if it truly is tiny enough that it would be a month long project… then the tooling is there
During the times we’re not using Clojure, we will be better Ruby devs for having done so
- Learning.
- Learning.
- Learning.
- … Ruby supports (and took!) a lot of abstractions from Functional languages and Lisps

So why not?

Learning new things is hard
- You need to learn FP and Lisp in one swoop
- I had a hard time reasoning about CLJ in my independent studies without spending time with Haskell first
- There’s a good chance OOP has broken your brain.
- It’s not always easy to reason about problems in new ways
- We are the next wave of BASIC programmers
  - … that was a Dijkstra joke
  - “It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they are mentally mutilated beyond hope of regeneration.”
- As a Rubyist that learning curve is lower
- You understand type dynamism
- You understand metaprogramming
- You understand higher order functions
  - Enummerable
  - Blocks, Procs, Lambdas, Object#method
- You probably care about programming if you’re here
Tooling
- Especially around Vim, it’s not quite there yet.
- …but if you know how to use Vim outside of a Rails app anyway, you’ll be fine
- Pure Clojure Libraries
- A lot of them are missing
- Sometimes interacting with a Java library can be clunky
  - If it becomes enough of a problem, write a wrapper around it. The Facilities for doing so are awesome.
Vulnerability
- You don’t know everything
- You need to admit and be in tune with this if you want to grow
- Making mistakes… probably more than you’re used to
- … but that’s okay
- I’m pretty sure you weren’t as bad ass as you are now when you first started with
  - Ruby or…
  - Objected Oriented Programming or…
  - Abstractions or…
  - Programming

Concrete, damn you!

I don’t know (every|any)thing either.
This becomes more apparent to me every day
Let’s look at some code
- https://github.com/rbxbx/clojure-as-a-service-example