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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<title>reveal.js</title>
<link rel="stylesheet" href="css/reveal.css">
<link rel="stylesheet" href="css/theme/black.css">
<!-- Theme used for syntax highlighting of code -->
<link rel="stylesheet" href="lib/css/zenburn.css">
<!-- Printing and PDF exports -->
<script>
var link = document.createElement( 'link' );
link.rel = 'stylesheet';
link.type = 'text/css';
link.href = window.location.search.match( /print-pdf/gi ) ? 'css/print/pdf.css' : 'css/print/paper.css';
document.getElementsByTagName( 'head' )[0].appendChild( link );
</script>
</head>
<body>
<div class="reveal">
<div class="slides">
<section>
<section data-markdown>
<script type="text/template">
</script>
</section>
<section data-markdown>
<script type="text/template">
## An Introduction to Erlang
Wait, what?
- Erlang is (was) an obscure programming language invented in the 80s by Ericsson
<!-- .element: class="fragment" -->
- Built to support telephony switching equipment at a global scale
<!-- .element: class="fragment" -->
- Designed to be distributed, concurrent, highly-available, fault-tolerant, and hot-swappable
<!-- .element: class="fragment" -->
- Can achieve 9 nine's of availability (31.5569 milliseconds of downtime per year)
<!-- .element: class="fragment" -->
- Unfortunately, it is an ugly, ugly language
<!-- .element: class="fragment" -->
</script>
</section>
<section data-markdown>
<script type="text/template">
## An Introduction to Elixir
- A compiled, dynamically-typed, functional language that supports metaprogramming
<!-- .element: class="fragment" -->
- Built on top of Erlang and compiles to the same byte-code
<!-- .element: class="fragment" -->
- Can utilize Erlang code/libraries
<!-- .element: class="fragment" -->
- Has all benefits of Erlang...
<!-- .element: class="fragment" -->
- ...but with a Ruby-like syntax
<!-- .element: class="fragment" -->
Prediction: Likely to replace Ruby/Rails over the next few years.
<!-- .element: class="fragment" -->
</script>
</section>
</section>
<section>
<section data-markdown>
<script type-"text/template">
## Basic Types
Elixir has 8 basic types, all of which are immutable.
</script>
</section>
<section data-markdown>
<script type="text/template">
## Integers
- Represent whole numbers
- Division of an Integer always produces a Float
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> 3 + 3
6
iex> 3 - 3
0
iex> 3 * 3
9
iex> 3 / 3
1.0
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Floats
- Represent decimal numbers
- Should not be trusted for important operations
<!-- .element: class="fragment" -->
- Third-party Decimal library should be used, may be promoted to standard library
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> 3.5 + 3.5
7.0
iex> 3.5 - 3.5
0.0
iex> 3.5 * 3.5
12.25
iex> 3.5 / 3.5
1.0
iex> 1.1 * 1.1
1.2100000000000002
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Booleans
- Represent logical propositions
- Comparisons do not support squishy concept of "truthiness"
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> true == true
true
iex> true == false
false
iex> true == 1
false
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Atoms
- Represent constant values
- Used primarily for programatic strings such as keys
<!-- .element: class="fragment" -->
- Boolean values are actually just Atoms
<!-- .element: class="fragment" -->
- Must follow variable naming unless quoted
<!-- .element: class="fragment" -->
- Should generally not be dynamically generated because of allocation limits in the language
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> :hello
:hello
iex> :true == true
true
iex> :1hello
** (SyntaxError) iex:17: unexpected token: ":"
iex> :"1hello"
:"1hello"
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Strings
- Are internally represented as UTF-8 binary byte lists
- Data length may not be the same as string length
<!-- .element: class="fragment" -->
- String module is UTF-8 aware
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> "hallå"
"hallå"
iex> String.to_charlist("hallå")
[104, 97, 108, 108, 229]
iex> IO.puts([104, 97, 108, 108, 229])
hallå
iex> String.length("hallå")
5
iex> Kernel.byte_size("hallå")
6
iex> String.upcase("hallå")
"HALLÅ"
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Lists
- Represent a set of values stored as a Linked List
- Item types can be mixed
<!-- .element: class="fragment" -->
- Can be concatenated and subtracted from each other
<!-- .element: class="fragment" -->
- Head/Tail operations on Lists are integral to the language for recursion
<!-- .element: class="fragment" -->
- Fast to prepend values, slow for everything else
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> Kernel.length([1, true, 2, false])
4
iex> ([1, true] ++ [2, false]) -- [true]
[1, 2, false]
iex> hd([1, true, 2, false])
1
iex> tl([1, true, 2, false])
[true, 2, false]
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Tuples
- Represent a set of values stored contiguously in memory
- Item types can be mixed
<!-- .element: class="fragment" -->
- Commonly used to return success/failure context from Functions
<!-- .element: class="fragment" -->
- Fast to read, slow to write
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> {:ok, 2}
{:ok, 2}
iex> Kernel.tuple_size({:ok, 2})
2
iex> Kernel.elem({:ok, 2}, 0)
:ok
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Functions
- Are first-class citizens which can be passed to, and returned from, other functions
- Are generally defined in Modules, but can be anonymous
<!-- .element: class="fragment" -->
- Are referenced by name + arity
<!-- .element: class="fragment" -->
- Final statement is implicit return, no explit returns
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> add = fn (n1, n2) -> n1 + n2 end
#Function<0.0000000/2 in :erl_eval.expr/5>
iex> add.(1, 2)
3
iex> Kernel.is_function(add)
true
iex> Kernel.is_function(add, 1)
false
iex> (&Kernel.is_function/2).(add, 2)
true
iex>
</code></pre>
</script>
</section>
</section>
<section>
<section data-markdown>
<script type-"text/template">
## Associative Types
In addition to the basic types, Elixir has two important associative types
that are simply basic types of a specific shape.
</script>
</section>
<section data-markdown>
<script type-"text/template">
## Keyword Lists
- Are Lists of two-element Tuples containing an Atom key and arbitrary value
- Commonly used for optional function arguments
<!-- .element: class="fragment" -->
- Keys are ordered, must be Atoms, and may be duplicated
<!-- .element: class="fragment" -->
- Key values are taken from the front
<!-- .element: class="fragment" -->
- The Keyword module provides functions for advanced operations
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> list = [{:a, 1}, {:b, 2}, a: 3]
[a: 1, b: 2, a: 3]
iex> list[:a]
1
iex> Keyword.get_values(list, :a)
[1, 3]
</code></pre>
</script>
</section>
<section data-markdown>
<script type-"text/template">
## Maps
- Keys are not ordered, can be of any type, and are unique
- Commonly used to represent structured data
<!-- .element: class="fragment" -->
- Are the basis for named structs
<!-- .element: class="fragment" -->
- The Map module provides functions for advanced operations
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> %{hello: "world"}.hello
"world"
iex> %{100 => "One Hundred"}[100]
"One Hundred"
iex> Map.keys(%{a: 1, b: 2})
[:a, :b]
iex> map = %{a: 1, b: 2}
%{a: 1, b: 2}
iex> %{map | b: 3}
%{a: 1, b: 3}
</code></pre>
</script>
</section>
</section>
<section>
<section data-markdown>
<script type="text/template">
## Operators
Elixir has all the normal operators you expect (+, -, /, *)
and a few that might look different...
</script>
</section>
<section data-markdown>
<script type="text/template">
## String Concatenation
<pre><code class="lang-elixir" data-trim>
iex> "Hello" <> " " <> "world"
"Hello world"
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Boolean Logic
- and, or, and not expect Boolean values
- &&, ||, and ! accept any value
<!-- .element: class="fragment" -->
- For the latter, anything that is not false or nil is "truthy"
<!-- .element: class="fragment" -->
<pre><code class="lang-elixir" data-trim>
iex> 1 and true
** (ArgumentError) argument error: 1
iex> 1 && true
true
iex> not nil
** (ArgumentError) argument error
:erlang.not(nil)
iex> !nil
true
iex> !"hello"
false
</code></pre>
</script>
</section>
</section>
<section>
<section data-markdown>
<script type="text/template">
## Pattern Matching
One of the most important aspects of the language.
Elixir does not have assignment, it has pattern matching and capturing.
<!-- .element: class="fragment" -->
The = operator is simply an equality assertion that either:
<!-- .element: class="fragment" -->
- Raises an error if the assertion fails; or
<!-- .element: class="fragment" -->
- Returns the right-hand value if it succeeds.
<!-- .element: class="fragment" -->
If a variable is present in the left-hand value, the equivalent right-hand value will be copied to it unless pinned.
<!-- .element: class="fragment" -->
</script>
</section>
<section data-markdown>
<script type="text/template">
## Pattern Matching Assertions
Returns the right-hand value if the pattern match succeeds
<!-- .element: class="fragment" data-fragment-index="1" -->
<pre class="fragment" data-fragment-index="1"><code class="lang-elixir" data-trim>
iex> {100, "X"} = {100, "X"}
{100, "X"}
</code></pre>
Raises a MatchError if it does not
<!-- .element: class="fragment" data-fragment-index="2" -->
<pre class="fragment" data-fragment-index="2"><code class="lang-elixir" data-trim>
iex> {100, ""} = Integer.parse("100X")
** (MatchError) no match of right hand side value: {100, "X"}
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Pattern Matching Captures
- Values from the right-hand side are copied to variables on the left-hand side if the overall pattern is matched
<!-- .element: class="fragment" data-fragment-index="1" -->
- Multiple and nested assertions are supported
<!-- .element: class="fragment" data-fragment-index="1" -->
- Effectively HIGH-ENERGY destructuring assignments
<!-- .element: class="fragment" data-fragment-index="2" -->
<pre class="fragment" data-fragment-index="1"><code class="lang-elixir" data-trim>
iex> ret = {n, "X"} = Integer.parse("100X")
{100, "X"}
iex> ret
{100, "X"}
iex> n
100
</code></pre>
Variables can be forced to match based on their value rather than capture using the ^ (pin) operator
<!-- .element: class="fragment" data-fragment-index="3" -->
<pre class="fragment" data-fragment-index="3"><code class="lang-elixir" data-trim>
iex> {:ok, ^n} = {:ok, 0}
** (MatchError) no match of right hand side value: {:ok, 0}
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Pattern Matching Lists
<pre><code class="lang-elixir" data-trim>
iex> [{:a, a_value} | rest] = [a: 1, b: 2, c: 3]
[a: 1, b: 2, c: 3]
iex> a_value
1
iex> rest
[b: 2, c: 3]
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Pattern Matching Maps
<pre><code class="lang-elixir" data-trim>
iex> %{type: :error, msg: m} = %{type: :error, msg: "Failure"}
%{message: "Failure", type: :error}
iex> m
"Failure"
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Pattern Matching Insanity
<pre><code class="lang-elixir" data-trim>
iex> ret = {:error, %{reasons: ["One", "Two"], count: 2}}
{:error, %{count: 2, reasons: ["One", "Two"]}}
iex> {:error = status, %{
reasons: [first | _rest] = all,
count: c
}} = ret
{:error, %{count: 2, reasons: ["One", "Two"]}}
iex> status
:error
iex> first
"One"
iex> all
["One", "Two"]
iex> c
2
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## SURPRISE
All of this can be used in function definitions to match/capture against parameters.
</script>
</section>
</section>
<section>
<section data-markdown>
<script type="text/template">
## Functions
Why we're all here, pay attention.
</script>
</section>
<section data-markdown>
<script type="text/template">
## Declaration
Inline:
<!-- .element: class="fragment" data-fragment-index="1" -->
<pre class="fragment" data-fragment-index="1"><code class="lang-elixir" data-trim>
iex> hello = fn(who) -> "Hello" <> " " <> who end
#Function<0.00000000/1 in :erl_eval.expr/5>
iex> hello.("World")
"Hello World"
</code></pre>
Module:
<!-- .element: class="fragment" data-fragment-index="2" -->
<pre class="fragment" data-fragment-index="2"><code class="lang-elixir" data-trim>
defmodule Greeter do
def hello(who), do: build_hello(who)
defp build_hello(who), do: "Hello #{who}"
end
</code></pre>
<pre class="fragment" data-fragment-index="2"><code class="lang-elixir" data-trim>
iex> Greeter.hello("World")
"Hello World"
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Oneliners vs Multiliners
One-liners can be good for readability if the function is simple
<!-- .element: class="fragment" data-fragment-index="1" -->
<pre class="fragment" data-fragment-index="1"><code class="lang-elixir" data-trim>
defmodule MyModule do
def one_liner(arg), do: arg <> " one"
end
</code></pre>
Multi-liners require an end
<!-- .element: class="fragment" data-fragment-index="2" -->
<pre class="fragment" data-fragment-index="2"><code class="lang-elixir" data-trim>
defmodule MyModule
def multi_liner(arg) do
arg = arg <> " multi"
arg
end
end
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Piping
Functions can be piped using the `|>` symbol similar to unix pipes where the
output of one function is passed as the first parameter to the next function.
<pre class="fragment"><code class="lang-elixir" data-trim>
defmodule IntegerOperator do
def add(n1, n2), do: n1 + n2
def sub(n1, n2), do: n1 - n2
def mult(n1, n2), do: n1 * n2
end
</code></pre>
<pre class="fragment"><code class="lang-elixir" data-trim>
iex> import IntegerOperator
IntegerOperator
iex> 10 |> add(1) |> mult(3) |> sub(2) |> add(5)
36
</code></pre>
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</section>
<section data-markdown>
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## Pattern Matches
- Functions can pattern match on parameters
<!-- .element: class="fragment" -->
- Functions with different pattern matches can share names, first match wins
<!-- .element: class="fragment" -->
<pre class="fragment"><code class="lang-elixir" data-trim>
defmodule Greeter do
def greet("Hello:" <> v2), do: "Hello #{v2}"
def greet({:ok, v1, v2}), do: {v1, v2}
def greet(%{key1: %{sub_key: v1}, key2: v2}), do: %{v1 => v2}
def greet(_), do: "Hello...you"
end
</code></pre>
<pre class="fragment"><code class="lang-elixir" data-trim>
iex> Greeter.greet("Hello:World")
"Hello World"
iex> Greeter.greet({:ok, "Hej", "Världen"})
{"Hej", "Världen"}
iex> Greeter.greet(%{key1: %{sub_key: "Hola"}, key2: "Mundo"})
%{"Hola" => "Mundo"}
iex> Greeter.greet(true)
"Hello...you"
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Guards
- Functions can put constraints on parameters using a subset of language operators and functions
<!-- .element: class="fragment" -->
- This includes variables pulled from pattern matches
<!-- .element: class="fragment" -->
<pre class="fragment"><code class="lang-elixir" data-trim>
defmodule Math do
def div(n1, n2)
when is_integer(n1) and is_integer(n2) and n2 != 0
do
n1 / n2
end
end
</code></pre>
<pre class="fragment"><code class="lang-elixir" data-trim>
iex> Math.div(9, "3")
** (FunctionClauseError) no function clause matching in Math.div/2
iex> Math.div(9, 0)
** (FunctionClauseError) no function clause matching in Math.div/2
iex> Math.div(9, 3)
3.0
</code></pre>
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</section>
<section data-markdown>
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## Recursion
Using all these tools, common programming problems can be reimagined as combinations
of simple functions.
<pre class="fragment"><code class="lang-elixir" data-trim>
defmodule IntegerFinder do
def first_neg([]), do: nil
def first_neg([h | _t]) when is_integer(h) and h < 0, do: h
def first_neg([_h | t]), do: first_neg(t)
end
</code></pre>
<pre class="fragment"><code class="lang-elixir" data-trim>
iex> IntegerFinder.first_neg([])
nil
iex> IntegerFinder.first_neg(["hello", "world"])
nil
iex> IntegerFinder.first_neg([1, 2, 3])
nil
iex> IntegerFinder.first_neg([1, 2, -4, 3])
-4
</code></pre>
</script>
</section>
</section>
<!--
<section>
<section data-markdown>
<script type="text/template">
## Modules
Are used to:
- Organize code
- Contain functions
- Define exceptions
- Define named structs
- Define contracts for other modules
<pre><code class="lang-elixir" data-trim>
defmodule MyModule do
# Module body would be defined here.
end
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Exceptions
- Take the name of the module they are defined in
- Are defined within a module using `defexception`
<pre><code class="lang-elixir" data-trim>
defmodule MyError do
defexception message: "Error"
end
</code></pre>
<pre><code class="lang-elixir" data-trim>
iex> raise MyError
** (MyError) Error
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Structs
- Take the name of the module they are defined in
- Are defined within a module using `defstruct`
- When declared, define the keys they support along with defaults for each key
<pre><code class="lang-elixir" data-trim>
defmodule Animal do
defstruct [type: :human, name: ""]
end
</code></pre>
<pre><code class="lang-elixir" data-trim>
iex> %Animal{name: "Daniel"}
%Animal{name: "Daniel", type: :human}
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## Behaviours
- Yes, it won't compile without the "u". ಠ_ಠ
- Define function signatures a module must implement to comply
<pre><code class="lang-elixir" data-trim>
defmodule Concatenator do
@callback concatenate(String.t, String.t) :: String.t
end
defmodule PipeConcatenator do
@behaviour Concatenator
def concatenate(s1, s2), do: s1 <> "|" <> s2
end
</code></pre>
<pre><code class="lang-elixir" data-trim>
iex> PipeConcatenator.concatenate("Hello", "World")
"Hello|World"
</code></pre>
</script>
</section>
</section>
-->
<section>
<section data-markdown>
<script type="text/template">
## Examples
Let's take a look at some common problems and how they could be solved the elixir way.
</script>
</section>
<section data-markdown data-transition="slide-in fade-out">
<script type="text/template">
## Projection (Javascript)
<pre><code class="lang-javascript" data-trim>
var IntegerProjector = {
addOne: function(numbers) {
var newNumbers = [];
for (var i = 0; i < numbers.length; i++) {
var n = numbers[i];
if (!(n === parseInt(n, 10))) {
throw new Error("Not an integer");
}
newNumbers.push(n + 1);
}
return newNumbers;
}
};
</code></pre>
</script>
</section>
<section data-markdown data-transition="fade-in slide-out">
<script type="text/template">
## Projection (Elixir)
<pre><code class="lang-elixir" data-trim>
defmodule IntegerProjector do
def add_one([]), do: []
def add_one([head | tail]) when is_integer(head) do
[head + 1] ++ add_one(tail)
end
end
</code></pre>
<pre class="fragment"><code class="lang-elixir" data-trim>
iex> IntegerProjector.add_one([])
[]
iex> IntegerProjector.add_one([1, "a"])
** (FunctionClauseError) no function clause matching in
IntegerProjector.add_one/1
iex:13: IntegerProjector.add_one(["a"])
iex:14: IntegerProjector.add_one/1
iex> IntegerProjector.add_one([1, 2, 3])
[2, 3, 4]
</code></pre>
</script>
</section>
<section data-markdown data-transition="slide-in fade-out">
<script type="text/template">
## Reduction (Javascript)
<pre><code class="lang-javascript" data-trim>
var IntegerReducer = {
sum: function(accumulator, numbers) {
for (var i = 0; i < numbers.length; i++) {
var n = numbers[i];
if (!(n === parseInt(n, 10))) {
throw new Error("Not an integer");
}
accumulator += n;
}
return accumulator;
}
};
</code></pre>
</script>
</section>
<section data-markdown data-transition="fade-in slide-out">
<script type="text/template">
## Reduction (Elixir)
<pre><code class="lang-elixir" data-trim>
defmodule IntegerReducer do
def sum(accumulator, []) when is_integer(accumulator) do
accumulator
end
def sum(accumulator, [head | tail])
when is_integer(accumulator) and is_integer(head)
do
sum((accumulator + head), tail)
end
end
</code></pre>
<pre class="fragment"><code class="lang-elixir" data-trim>
iex(16)> IntegerReducer.sum(10, [])
10
iex(17)> IntegerReducer.sum(10, ["a"])
** (FunctionClauseError) no function clause matching in
IntegerReducer.sum/2
iex:16: IntegerReducer.sum(10, ["a"])
iex(17)> IntegerReducer.sum(10, [1, 2, 3])
16
</code></pre>
</script>
</section>
<section data-markdown>
<script type="text/template">
## HTTP Response Handling
<pre><code class="lang-elixir" data-trim>
defmodule Getter
alias HTTPoison.Response as R
def get(url), do: url |> make_request |> handle_response
defp make_request(url), do: HTTPoison.get!(url)
defp handle_response(%R{status_code: code, headers: headers})
when code in [301, 302]
do
get(headers["Location"])
end
defp handle_response(%R{status_code: 404}) do
{:error, :not_found}
end
defp handle_response(%R{status_code: 200, body: body}) do
{:ok, body}
end
defp handle_response(_), do: {:error, :unhandled}
end
</code></pre>
</script>
</section>
</section>
<section>
<section data-markdown>
<script type="text/template">
## Closing it out
There is so much more to Elixir
- Distributed execution of code across nodes
<!-- .element: class="fragment" -->
- Lightweight concurrency through the Language Process model
<!-- .element: class="fragment" -->
- In-place, hot-swappable code changes without system process restarts
<!-- .element: class="fragment" -->
- Fault-tolerant recovery of crashed Language Processes with no downtime
<!-- .element: class="fragment" -->
- Metaprogramming that allows for extending the language at compile-time
<!-- .element: class="fragment" -->
</script>
</section>
</section>
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