Elixir – Belarus Ruby User Group 25 Jan 2014

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Elixir Сергей Нартымов Brainspec https://github.com/lest twitter: @just_lest

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Elixir is a metaprogrammable, functional language built atop the Erlang VM.

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Elixir

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Metaprogramming

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Metaprogramming iex> nil?(1) false iex> nil?(nil) true defmacro nil?(x) do quote do: unquote(x) == nil end

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Metaprogramming iex> nil?(1) false iex> nil?(nil) true defmacro nil?(x) do quote do: unquote(x) == nil end

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Metaprogramming if(foo, do: bar, else: baz) if foo do bar else baz end

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Metaprogramming defmacro unless(clause, options) do do_clause = Keyword.get(options, :do, nil) else_clause = Keyword.get(options, :else, nil) quote do if(unquote(clause), do: unquote(else_clause), else: unquote(do_clause)) end end

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Metaprogramming Lisps traditionally empowered developers because you can eliminate anything that’s tedious through macros, and that power is really what people keep going back for. — Rich Hickey

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Functions

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Function capture iex> list = ["foo", "bar", "baz"] ["foo","bar","baz"] iex> Enum.map list, fn(x) -> size(x) end [3,3,3] iex> Enum.map list, &size/1 [3,3,3] iex> fun = &rem(&1, 2) #Function<6.80484245 in :erl_eval.expr/5> iex> fun.(4) 0

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Partial application iex> list = ["foo", "bar", "baz"] ["foo","bar","baz"] iex> Enum.map list, fn(x) -> size(x) end [3,3,3] iex> Enum.map list, &size/1 [3,3,3] iex> fun = &rem(&1, 2) #Function<6.80484245 in :erl_eval.expr/5> iex> fun.(4) 0

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Pipeline operator

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f3(f2(f1(state))) state |> f1 |> f2 |> f3

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f3(f2(f1(state))) state |> f1 |> f2 |> f3

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list |> Enum.filter(&(&1 > 0)) # take positive numbers |> Enum.map(&(&1 * &1)) # square each one |> Enum.reduce(0, &(&1 + &2)) # calculate sum

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Polymorphism

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Protocols

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Protocols defprotocol Inspect do def inspect(thing, opts) end defimpl Inspect, for: Atom do def inspect(false), do: "false" def inspect(true), do: "true" def inspect(nil), do: "nil" def inspect(atom) do # ... end end

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Protocols defimpl Inspect, for: List do # ... end defimpl Inspect, for: Integer do # ... end

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ExUnit A unit test framework

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ExUnit ExUnit.start defmodule MyTest do use ExUnit.Case test "the truth" do assert true end end $ elixir assertion_test.exs

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ExUnit ExUnit.start defmodule MyTest do use ExUnit.Case test "the truth" do assert true end end $ elixir assertion_test.exs

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ExUnit assert 1 + 1 == 2 refute 1 + 3 == 3 assert 1 + 1 == 3 # Expected 2 to be equal to (==) 3

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Mix A build tool

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Mix defmodule MyProject.Mixfile do use Mix.Project def project do [ app: :my_project, version: "0.0.1", deps: deps ] end # Configuration for the OTP application def application do [] end defp deps do [] end end

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Mix defp deps do [ { :some_project, github: "some_project/other", tag: "0.3.0" }, { :another_project, ">= 1.0.2", git: "https://example.com/another/repo.git" } ] end

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Other

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Other • Unicode strings

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Other • Unicode strings • String sigils, heredocs

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Other • Unicode strings • String sigils, heredocs • Documentation

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Other • Unicode strings • String sigils, heredocs • Documentation • List comprehentions

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Resources • http://elixir-lang.org/ • http://joearms.github.io/2013/05/31/a-week- with-elixir.html • http://www.theerlangelist.com/2014/01/ why-elixir.html • http://devintorr.es/blog/2013/06/11/elixir- its-not-about-syntax/

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Спасибо https://github.com/lest twitter: @just_lest Сергей Нартымов Brainspec