Awesome

elm-ui-rocks

Learning to use elm-ui by building a simple rock, paper, scissors game

npm install elm-ui -g

git clone https://github.com/run-time/elm-ui-rocks.git

cd elm-ui-rocks

elm-ui install

elm-ui server

http://localhost:8002

GOALS

Fix the score to keep a running total of wins / losses
Fix game results to show notifications after each button click
Add buttons for Lizard and Spock
Show instructions on initial page load

ELM INTRO

The Elm programming language has too many awesome features to list here so work your way through the docs at -- http://elm-lang.org/docs

Here are my 3 favorite things about Elm so far...

Everything is a function! (okay, not really but all the good stuff is) Even my favorite number 4 is a function which always returns a number and that number always happens to be my favorite number. How cool is that?!

Run elm-repl from a terminal window to test it out...
```
  > 4
  4 : number
  > four = 4
  4 : number
  > four
  4 : number
```
Zero run-time errors! Since Elm is a strongly typed language it won't compile down to JavaScript if there are any ambiguities in the code.
Currying is built-in to the language! Currying is so fundamental to functional programming Elm does it using the best interface ever -- whitespace! I often say, "the best UI is no UI" and although Elm is rigid when it comes to actual data-types the type syntax is clean and flexible.

We can define an Elm function which adds two numbers together like so...
```
  add : number -> number -> number
  add a b =
    a + b
```
Although the arrow type system in Elm may seem a little peculiar at first it is one of my favorite things about the syntax. The function return type is always at the end so in this case our function actually has 3 return types depending on how it's called!

If we pass in two numbers add returns a number If we pass in one number add returns a number -> number If we pass in zero numbers add returns a number -> number -> number

It's time to break out the elm-repl again...
```
  > add
  <function> : number -> number -> number
  > add 1
  <function> : number -> number
  > add 2 3
  5 : number
```
It takes some practice using small functions to create bigger and bigger functions but the Elm syntax can really help lower the barrier to entry.

Let's see an example starting with our fundamental add function...
```
  increment : number -> number
  increment a =
    add a 1
```
Using the elm-repl we can see this in action...
```
  > increment
  <function> : number -> number
  > increment 3
  4 : number
```
And we can also see that even the + operator is just a function!
```
  > (+)
  <function> : number -> number -> number
  > (+) 2 2
  4 : number
```
Which brings us back to -- 1. Everything is a function!