Elixir - Not Just For Rubyists

An introduction to the Elixir language presented at the Belfast Elixir Group.

Transcript

1. NOT JUST FOR RUBYISTS ELIXIR
2. ELIXIR
3. INTRO WHAT ARE WE HERE FOR? ▸ An overview of the Elixir language and the Erlang VM ▸ A tour of some of the most interesting features of the language ▸ A diversion into the Elixir development environment
4. INTRO WHO THE F**K IS THIS GUY? ▸ Maurice Kelly ▸ @mo in the NI Tech Slack ▸ Professional programmer since 2001 ▸ Dabbled in a few languages BASIC
 |> C
 |> PHP
 |> C++
 |> Java
 |> Objective-C
 |> Swift
 |> Elixir
5. INTRO WHAT DID RUBYISTS EVER DO TO YOU? ▸ Elixir has a Ruby heritage ▸ Elixir has a distinctly Ruby style def, do, end, puts, and lots of :atoms ▸ Elixir is popular with Rubyists for experimentation ▸ But it’s not just for Rubyists!
6. INTRO WHAT DID RUBYISTS EVER DO TO YOU? ▸ Elixir has a Ruby heritage ▸ Elixir has a distinctly Ruby style def, do, end, puts, and lots of :atoms ▸ Elixir is popular with Rubyists for experimentation ▸ But it’s not just for Rubyists!
7. INTRO WHAT DID RUBYISTS EVER DO TO YOU? ▸ Elixir has a Ruby heritage ▸ Elixir has a distinctly Ruby style def, do, end, puts, and lots of :atoms ▸ Elixir is popular with Rubyists for experimentation ▸ But it’s not just for Rubyists!
8. INTRO WHAT DID RUBYISTS EVER DO TO YOU? ▸ Elixir has a Ruby heritage ▸ Elixir has a distinctly Ruby style def, do, end, puts, and lots of :atoms ▸ Elixir is popular with Rubyists for experimentation ▸ But it’s not just for Rubyists!
9. WHAT IS ELIXIR?
10. COMPILED
11. RUNS ON THE ERLANG VM
12. RUNS ON THE ERLANG VM
13. RUNS ON THE ERLANG VM
14. DYNAMIC AND STRONGLY TYPED
15. DYNAMIC AND STRONGLY TYPED
16. FUNCTIONAL
17. FUNCTIONAL
18. WHAT IS IT LIKE?
19. WAFFLE FUNCTIONS ▸ Functions are the building block for Elixir code int sumTwoNumbers( int a, int b ) { // Java
 return a + b;
 } def sum_two_numbers( a, b ) do # Elixir
 a + b
 end
20. WAFFLE FUNCTIONS ▸ Functions can also contain conditions ▸ In this example we want a special case where we are summing two number that are equal def sum_two_numbers( a, b ) when a == b do
 a * 2
 end
 
 def sum_two_numbers( a, b ) do
 a + b
 end
21. WAFFLE MODULES ▸ Elixir groups functionality by modules defmodule SimpleMath do
 def sum_two_numbers( a, b ) do
 a + b
 end
 end
22. WAFFLE MODULES ▸ Modules can be nested defmodule SimpleMath do
 defmodule Summing do
 end
 end ‣ This doesn’t imply a special relationship - it is purely visual defmodule SimpleMath do
 end defmodule SimpleMath.Summing do
 end
23. WAFFLE IMMUTABILITY ▸ Everything is immutable var array = [“One”, “Two”, “Three”] // Swift
 array = array + “Four”
 print(array) // [“One”, “Two”, “Three”, “Four”] array = ["One", "Two", “Three"] # Elixir
 array ++ ["Four"]
 array # ["One", "Two", “Three"] array = array ++ [“Four”] # Elixir
 array # [“One”, “Two”, “Three”, “Four”]
24. WAFFLE PATTERN MATCHING ▸ Based on the match operator — = {a, b, c} = {1, 2, 3} ▸ Results in a = 1, b = 2 and c = 3 ▸ Pattern matching is used throughout Elixir ▸ Particularly important for ▸ function selection ▸ case statements ▸ message passing and more
25. WAFFLE PATTERN MATCHING - CASE STATEMENTS ▸ if statements are available, but not used extensively ▸ Elixir code relies more on case statements if (a == 1) { // Swift
 return true
 } else if (a == 2 && b > 1) {
 return true
 } else {
 return false
 } case {a, b} do # Elixir
 {1, _} -> true
 {2, x} when x > 2 -> true
 _ -> false
 end
26. WAFFLE PATTERN MATCHING - FUNCTIONS def sum_two_numbers( a, b ) when a == b do
 a * 2
 end def sum_two_numbers( a, b ) do
 a + b
 end ‣ Can also match specific values: def sum_two_numbers( a, 0 ) do
 a
 end
27. WAFFLE PIPELINE OPERATOR ▸ An operator to take lifeless code and make it sleeker, shinier, and more free flowing. initial_string = “HELLO WORLD!” # Ruby
 first_step = lowercase(initial_string)
 second_step = titlecase(first_step)
 result = trim(second_step, “!”) initial_string = “HELLO WORLD!” # Elixir
 first_step = String.downcase(initial_string)
 second_step = String.capitalize(first_step)
 result = String.trim_trailing(second_step, "!")
28. WAFFLE PIPELINE OPERATOR ▸ An operator to take lifeless code and make it sleeker, shinier, and more free flowing. initial_string = “HELLO WORLD!” # Ruby
 first_step = lowercase(initial_string)
 second_step = titlecase(first_step)
 result = trim(second_step, “!”) result = “HELLO WORLD!” # Elixir
 |> String.downcase
 |> String.capitalize
 |> String.trim_trailing(“!”)
29. WAFFLE STATEFUL PROCESSES ▸ The only state in Elixir is that which you pass around ▸ Erlang processes can act as containers for state ▸ Messages can be used to “modify” the state within a process
30. WAFFLE STATEFUL PROCESSES ▸ In this example we try to process an :increment message receive do
 :increment ->
 new_state = state + 1
 end ▸ This only processes one message at a time
31. WAFFLE STATEFUL PROCESSES ▸ In this example we try to process an :increment message def loop() do
 receive do
 :increment ->
 new_state = state + 1
 loop()
 end
 end ▸ The state doesn’t go anywhere
32. WAFFLE STATEFUL PROCESSES ▸ In this example we try to process an :increment message def loop(state) do
 receive do
 :increment ->
 new_state = state + 1
 loop(new_state)
 end
 end ▸ The updated state is ready for the start of each message received
33. WAFFLE RECURSION ▸ Elixir dispenses with while and for loops ▸ Conditional functions help def recursive_function(value) when value is_map() do
 end def recursive_function(value) when value is_list() do
 end def recursive_function(value) do
 end
34. WAFFLE RECURSION ▸ As does tail call optimisation def recursive_function(value) do
 ... recursive_function(new_value)
 end ‣ The last expression in the body must be a recursive call
35. DEV ENVIRONMENT
36. ALTERNATIVE FACTS HOW DO I GET STARTED WITH ELIXIR? ▸ Mac - brew install elixir ▸ Linux - yum install elixir or apt-get install elixir ▸ Windows - an official installer exists — https://repo.hex.pm/elixir-websetup.exe ▸ Source ▸ git clone https://github.com/elixir-lang/elixir.git ▸ cd elixir ▸ make clean test
37. ALTERNATIVE FACTS IS THERE AN IDE?
38. ALTERNATIVE FACTS IS THERE AN IDE? ▸ Vim
39. ALTERNATIVE FACTS IS THERE AN IDE? ▸ Vim ▸ Atom
40. ALTERNATIVE FACTS IS THERE AN IDE? ▸ Vim ▸ Atom ▸ VS Code
41. ALTERNATIVE FACTS IS THERE AN IDE? ▸ Vim ▸ Atom ▸ VS Code ▸ IntelliJ
42. ALTERNATIVE FACTS HOW DO I BUILD ELIXIR APPLICATIONS? ▸ Scripts can be run directly $ elixir your_script.exs ▸ The Mix tool is the best way to manage bigger applications and can: ▸ build and test ▸ manage dependencies ▸ create new projects or resources within projects
43. ALTERNATIVE FACTS HOW DO I BUILD ELIXIR APPLICATIONS? ▸ Scripts can be run directly $ elixir your_script.exs ▸ The Mix tool is the best way to manage bigger applications and can: ▸ build and test ▸ manage dependencies ▸ create new projects or resources within projects
44. ALTERNATIVE FACTS DOES IT HAVE A REPL? ▸ The Elixir REPL is called Iex (eye-ee-ex, not Lex) $ iex
 Erlang/OTP 19 [erts-8.2] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]
 
 Interactive Elixir (1.4.0) - press Ctrl+C to exit (type h() ENTER for help)
 iex(1)> ▸ You can load your project directly into Iex: $ iex -S mix
45. ALTERNATIVE FACTS HOW DO I RUN MY APPLICATIONS?
46. ALTERNATIVE FACTS HOW DO I RUN MY SCRIPTS ▸ Scripts don’t need to be precompiled $ elixir your_script.exs ▸ This does the following: ▸ Compiles the script into bytecode in memory ▸ Starts the BEAM with the bytecode ▸ Cleans everything up when the script is done
47. ALTERNATIVE FACTS HOW DO I RUN MY COMMAND-LINE TOOL? ▸ Non-trivial command line tools can be bundled as an escript ▸ Requires a change to mix.exs to include this configuration: escript: [main_module: EntryPointModuleName] ▸ On launch the function main/1 in that module will receive the arguments ▸ Build using mix escript.build ‣ https://hexdocs.pm/mix/master/Mix.Tasks.Escript.Build.html
48. ALTERNATIVE FACTS HOW DO I RUN MY SERVER? ▸ Long-lived processes need to define an application callback function: mod: {ApplicationEntryPoint, []} ▸ This executes the start/2 function in the ApplicationEntryPoint module ▸ To launch: $ mix run
49. ALTERNATIVE FACTS WHAT ABOUT TESTING? ▸ ExUnit defmodule ModuleTest do
 use ExUnit.Case # brings in test functionality
 doctest Module # module should be doc-tested
 test "the truth" do # the start of a test
 assert 1 + 1 == 2 # a test assertion
 end
 end ‣ Doctests
50. ALTERNATIVE FACTS WHAT ABOUT TESTING? describe “when the app is doing something” do
 test “it does this” do
 end
 
 test “it does that too” do
 end
 end ‣ Tests should be named as .exs and are run using mix test ‣ Doctests
51. ALTERNATIVE FACTS SO HOW DO I MANAGE DEPENDENCIES? ▸ Hex (https://hex.pm) defp deps do
 [{:cowboy, "~> 1.0.3"},
 {:plug, "~> 1.0”}]
 end ▸ Hex is pulled in and invoked by Mix mix deps.get ▸ Documentation available at https://hexdocs.pm
52. ALTERNATIVE FACTS SO HOW DO I MANAGE DEPENDENCIES? ▸ Hex (https://hex.pm) defp deps do
 [{:cowboy, "~> 1.0.3"},
 {:plug, "~> 1.0”}]
 end ▸ Hex is pulled in and invoked by Mix mix deps.get ▸ Documentation available at https://hexdocs.pm
53. INTERESTED?
54. HAPPY FINISH WRAPPING UP ▸ Elixir is a modern, concurrent and functional programming language that compiles down to bytecode suitable for execution on the Erlang VM. ▸ It relies on the many years of development put into the Erlang VM to provide a scalable, distributed and fault-tolerable execution environment. ▸ As a developer, I really enjoying working with it. ▸ I think you might too.
55. HAPPY FINISH LINKS AND RESOURCES ▸ elixir-lang.org — main project site ▸ elixir-slackin.herokuapp.com — Community Slack ▸ nitech.herokuapp.com — NI Tech Slack - #elixir ▸ www.belfastelixir.org — the site for this meetup ▸ elixirsips.com — lots of training material ▸ @mauricerkelly — @belfastelixir ▸ manning.com/books/the-little-elixir-and-otp-guidebook — Little Elixir & OTP Guidebook