What is Elm?

Funct lang
Compiled
For the Web

Why Elm?

Not Javascript
Fast
Good practices

• Has no side effects
• No state values
• Has attributes
• Return depends only on input

// There is an state.
var counter = 1;

function addCounterAndIncreaseIt(num) {
    // Output does not depend only on input.
    num += counter;

    // Has a side effect.
    counter++;

    return num;
}

var a = addCounterAndIncreaseIt(1);

// a is 2.
// counter is 2.

var b = addCounterAndIncreaseIt(1);

// b is 3.
// counter is 3.

function add(a, b) {
    return a + b;
}

var a = add(1, 2);
var b = add(1, 2);

// a is 3.
// b is 3.

Setting up the environment

npm install -g elm

What comes with Elm?

REPL

An interactive shell that lets you interact with values and functions directly.

Reactor

Dinamically compiles Elm files on demand and starts a server to test them on the browser.

Make

The Elm compiler.

Generates the HTML or JavaScript output.

Package

Package manager.

• Downloads dependencies.
• Publishes packages.
• Updates dependencies.
• Shows differences between versions

• Only handles contributed packages
• Enforces semantic versioning
• Find them at http://package.elm-lang.org/

That's pretty cool but...

SHOW
ME THE
CODE!

Elm Variable Types

• String
• Char
• Bool
• Float
• Int
• Lists
• Tuples
• Objects?

Elm Records

Elm Records

Kind of a JS object

• Fields most exists
• Cannot be null
• Group of related fields
• No self references

Null, I call it my billion-dollar mistake

Tony Hoare, inventor of null

Type aliases

That's all folks!

Questions?