An introduction to Elm
Some rules
- This is not a class. Interrumpt me!
- Do you have a question? Ask away!
- I might be wrong. Correct me!
Disclaimer
- I am no expert
- I am backend developer
- I actually do mostly PHP
- You will see some serius bad jokes
Before we get started
Let's get rid of something
An Elm developer
is an Elmo
Something about me
What is Elm?
Funct lang
Compiled
For the Web
Why Elm?
Not Javascript
Fast
Good practices
What is Functional Programing?
Almost exclusive use of Pure Functions
What is a Pure Function?
- Has no side effects
- No state values
- Has attributes
- Return depends only on input
Why Pure Functions?
- Reusable
- Composable
- Testable
- Cacheable
- Parallelizable
- ...
Functional Programming
VS
Functional Programming Languages
Setting up the environment
npm install -g elm
alias elm='docker run -it --rm -v "$(pwd):/code" -w "/code" -e "HOME=/tmp" -u $UID:$GID -p 8000:8000 codesimple/elm:0.17'
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
A bit more about packages
- Only handles contributed packages
- Enforces semantic versioning
- Find them at http://package.elm-lang.org/
That's pretty cool but...
SHOW
ME THE
CODE!
Let's write some
FUNCTIONS!
Partial applications
Forward pipe operator
|>
Anonymous functions
Let ... In ...
Prefix functions
VS
Infix functions
Function composition
Elm Static Types
- Types are inferred
- Friendly errors
- No runtime exceptions
Totally not
JAVA
Elm Variable Types
What types do you know?
- String
- Char
- Bool
- Float
- Int
- Lists
- Tuples
- Objects?
Elm Records
Elm Records
Kind of a JS object
Some rules
- Fields most exists
- Cannot be null
- Group of related fields
- No self references
Accesing properties
Updating properties
Are we missing something?
Where is the
null?
null is null
I mean... There is no null
Null, I call it my billion-dollar mistake
Tony Hoare, inventor of null
Union types
A value that could be of multiple types
Union types
Pattern matching
Maybe and Result
Type aliases
Just do it!
The Elm Architecture
Like Redux but without JS
(Also called Flux)
That's all folks!
Questions?
Some resources
Some examples
Some spam
An introduction to Elm
By david_hernandez
