Distill

Kasun Vithanage

The world is scary

Anything can go wrong

Yes, anything

  • Your network can go down
  • Harddisk can fail
  • Packets might be lost
  • There can be unhandled errors
  • etc...

Some Systems cannot go down

That easily

  • Telephone Systems
  • Network Systems
  • Nuclear Weapon Systems
  • Healthcare Systems
  • Banking Systems
  • etc...

A Problem In Telecom

  • Telecom Systems need to be reliable and highly available(non-stop)
  • At that time(in the 80s) telephone switches were written using C
  • Upgrading the software of these switches was hard
    • Specially when people still calling someone all the time
  • People at Ericcson wanted to solve this problem

was born 🎂

  • Erlang was created by Joe Armstrong, Robert Virding and Mike Williams in 1980
  • The first implementation was in Prolog
  • Later it was implemented in C
  • Syntax was similar to Prolog 😪
  • The virtual machine that runs Erlang Code is known as BEAM VM
Joe A

Joe Armstrong

Traits of Erlang

  • A Functional Language
  • Distributed
  • Concurrent
  • Fault Tolerant
  • Low-Latency
  • Robust

This makes Erlang suitable for

Soft-Realtime Systems 😚

  • Immutability
  • Process Isolation
  • Message Passing
  • Pattern Matching

It also has

Erlang in Action

Factorial

In Mathematics

n! = n \cdot(n - 1) \cdot(n - 2) \cdot... \cdot 2\cdot 1 \\ n! = n\cdot(n - 1)!

In Erlang

% module definition
-module(fact). 
-export([fac/1]).

fac(0) -> 1;
fac(N) when N > 0, is_integer(N) -> N * fac(N-1).

"Small" Companies Using Erlang

  • WhatsApp
  • Cisco
  • Goldman Sachs
  • Heroku
  • Nintendo
  • Riot Games(For LoL Chat)
  • Klarna.

More from here

José was a RoR(Ruby on Rails) contributor.

 

He wanted to make it safe and performant 🚀

 

Instead, he ended up creating a new programming language 😬

So dont be like him, please 😰

No, I'm kidding... 

José Valim

Elixir has a modern clean look, its like reading English 😎

Finally, you can use all cores of your VPS or whatever to run your dream app which scales to millions of users 😍

Of course, it's functional...but you don't need to learn Monads, Functors or do a PhD to understand code 🤓

Fortunately, it compiles to Erlang BEAM bytecodes, so you can access the Erlang ecosystem without any problem 🎉

Only "small" Companies uses Elixir 😏

  • Discord
  • Heroku
  • Change.org
  • Pinterest
  • PepsiCo
  • XPlane
  • Slab
  • Adobe

More from here

Ok Let's make a potion

Basic Data Types

  • Integers
    • 123
    • 0b100
    • 0xFA
    • 0o56
  • Floats
    • 64-bit double precision
    • 0.112
    • 1.0e-10
  • Atoms(or Symbols)
    • Represents distinct values
    • :ok, :error
    • true, false, nil are special atoms
  • Strings
    • Strings are double quoted
    • "hello world"
    • UTF-8 Supported
    • Single quoted values represent charlists
  • Booleans
    • true or false
    • 1 == 1 is true
    • 1 == 3 is false
  • Tuples
    • {:ok, "1", 1.2} is a tuple
    • They can hold any value
    • Contiguously stored in memory
    • Often used to return multiple values
  • Lists
    • [1, 2, "3", 4.4] is a list
    • Stored as a Linked List in memory
    • Prepending to list is fast, Appending is slow

Where are Functions?

Yes, Elixir has first-class support for functions

Anonymous functions

  • Starts with fn and ends with end
  • To invoke, you need to use a dot(.)
    • add.(1, 2)would give 3
  • Parenthesis are optional
  • Number of arguments for functions known as arity of the function
    • add/2 means add has 2 args
  • We will discuss about named functions
add = fn a, b -> a + b end

IO.puts(add.(1, 2))

Some Basic Operators

Basic Arithmetic

Operators like +, -, / and * are used with numerical types.

div, rem can be used with integer division

List Operators

++ and -- can be used to manipulate lists

iex(1)> [1, 2, 3] ++ [4, 5]
[1, 2, 3, 4, 5]
iex(2)> [1, 2, 3] -- [1]
[2, 3]

<> is used to concat strings

String Operators

iex(1)> "hello" <> "world"
"helloworld"

Binary Operators

Operators like and, or, not used with boolean values only

 

&&, ||, ! will work with any value. Everything except nil or false will be evaluated to truthy

Pattern Matching

= in Elixir is called Match Operator.

It can match left side and right side.

iex> x = 1
1
iex> 1 = x
1
iex> 1 = y # since y is not defined, we cant match this.
** (CompileError) iex:11: undefined function y/0 (there is no such import)

When you write x = 1, elixir will bind value 1 to variable x.

You can also rebind x to another value later as well.

iex> x = 1
1
iex> x = "wave"
"wave"
iex> x = "zync"
"zync"
iex> x
"zync"

Match operator works on complex values as well

iex> {a, b, c} = {:hello, "world", 123}
{:hello, "world", 123}
iex> a
:hello
iex> b
"world"
iex> c
123

With Tuples

iex> list = [1, 2, 3, 4, 5]
[1, 2, 3, 4, 5]
iex> [head | tail] = list
[1, 2, 3, 4, 5]
iex> head
1
iex> tail
[2, 3, 4, 5]

With Lists

If you want to match against an existing value without rebinding ^ (pin operator) is your friend

iex> x = 1
1
iex> ^x = 2
** (MatchError) no match of right hand side value: 2

iex> {a, ^x, b} = {1, 3, 1}
** (MatchError) no match of right hand side value: {1, 3, 1}

iex> {a, ^x, b} = {1, 1, 1}
{1, 1, 1}

You can do cool stuffs with Elixir

More Data Structures 😎

Keyword Lists

Keyword List is a special list of two element tuples

iex> [{:hello, "world"}, {:age, 25}]
[hello: "world", age: 25]
iex> [hello: "world", age: 25]   
[hello: "world", age: 25]

There are 3 special charasteristics

  • Keys must be atoms
  • Keys are ordered, as specified by the developer
  • Keys can be given more than once

This is really useful when passing options to functions

Maps

Maps are the "Go To" data structure in Elixir

Maps can have any value as keys

Maps also don't follow any ordering

iex> my_map = %{:hello => "world", "hi" => "elixir", 1 => 2}
%{1 => 2, :hello => "world", "hi" => "elixir"}
iex> my_map[:hello]
"world"
iex> my_map["hi"]  
"elixir"
iex> my_map[1]   
2

Control Structures

if and unless

Elixir doesn't have those built into the language, instead they are macros

iex> if String.length("hello") == 5 do
...>     "its five"                   
...> else                             
...>     "oh no"                      
...> end
"its five"

unless is the opposite of if

iex> unless String.length("hello") == 5 do
...>    "oh no"
...> else
...>    "its five"
...> end
"its five"

Note that there is no return keyword.

case

if/unless works with boolean or nil only

case brings power of pattern matching into the play

iex> case {1, 2, 3} do
...>     {1, x, 3} -> "matches x and binds it to 2"
...>     _ -> "nothing matches any clause"
...> end
"matches x and binds it to 2"

We can be more selective with guards

iex> case {1, 2, 3} do
...>     {1, x, 3} when x > 0 -> "matches x and binds it to 2"
...>     _ -> "nothing matches any clause"
...> end
"matches x and binds it to 2"

You can apply multiple guards to same clause

Not only in case, multiple clauses can be used with functions too

iex> add = fn                                             
...>     x, y when is_number(x) and is_number(y) -> x + y 
...>     x, y when is_binary(x) and is_binary(y) -> x <> y 
...>     x, y -> "hmm not sure what to do"                
...> end
#Function<13.126501267/2 in :erl_eval.expr/5>
iex> add.(100, 1)
101
iex> add.("hello", "elixir")
"helloelixir"
iex> add.("hi", 1)
"hmm not sure what to do"

Note that is_number and is_binary are guards

You can also write custom guards 💂‍♂️

With anonymous functions, you need to maintain same aritey 🤓

cond

This is similar to if/else if in other langs.

iex> cond do 
...>    1 == 1 -> "its true, i knew it"
...>    :a == false -> "who is the imposter"
...> end
"its true, i knew it"

This is not widely used with elixir

But its there just in case 😏

Did you notice something?

Every statement returns a value.

Yes, even if, cond, case too

So we can write code like this 😎

iex> result = case {1, 2, 3} do   
...>    {1, x, 3} -> x * 10
...>    {x, x, x} -> x * 3 # it matches when all elems are same    
...>    _ -> 100
...> end
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