diff options
Diffstat (limited to 'elixir.html.markdown')
| -rw-r--r-- | elixir.html.markdown | 60 |
1 files changed, 56 insertions, 4 deletions
diff --git a/elixir.html.markdown b/elixir.html.markdown index 0a20e3df..a74baa38 100644 --- a/elixir.html.markdown +++ b/elixir.html.markdown @@ -3,6 +3,8 @@ language: elixir contributors: - ["Joao Marques", "http://github.com/mrshankly"] - ["Dzianis Dashkevich", "https://github.com/dskecse"] + - ["Ryan Plant", "https://github.com/ryanplant-au"] + - ["Ev Bogdanov", "https://github.com/evbogdanov"] filename: learnelixir.ex --- @@ -91,6 +93,19 @@ string. <<1,2,3>> <> <<4,5>> #=> <<1,2,3,4,5>> "hello " <> "world" #=> "hello world" +# Ranges are represented as `start..end` (both inclusive) +1..10 #=> 1..10 +lower..upper = 1..10 # Can use pattern matching on ranges as well +[lower, upper] #=> [1, 10] + +# Maps are key-value pairs +genders = %{"david" => "male", "gillian" => "female"} +genders["david"] #=> "male" + +# Maps with atom keys can be used like this +genders = %{david: "male", gillian: "female"} +genders.gillian #=> "female" + ## --------------------------- ## -- Operators ## --------------------------- @@ -113,7 +128,8 @@ rem(10, 3) #=> 1 # These operators expect a boolean as their first argument. true and true #=> true false or true #=> true -# 1 and true #=> ** (ArgumentError) argument error +# 1 and true +#=> ** (BadBooleanError) expected a boolean on left-side of "and", got: 1 # Elixir also provides `||`, `&&` and `!` which accept arguments of any type. # All values except `false` and `nil` will evaluate to true. @@ -165,7 +181,7 @@ case {:one, :two} do {:four, :five} -> "This won't match" {:one, x} -> - "This will match and bind `x` to `:two`" + "This will match and bind `x` to `:two` in this clause" _ -> "This will match any value" end @@ -190,7 +206,7 @@ cond do "But I will" end -# It is common to see the last condition equal to `true`, which will always match. +# It is common to set the last condition equal to `true`, which will always match. cond do 1 + 1 == 3 -> "I will never be seen" @@ -311,6 +327,14 @@ defmodule MyMod do IO.inspect(@my_data) #=> 100 end +# The pipe operator |> allows you to pass the output of an expression +# as the first parameter into a function. + +Range.new(1,10) +|> Enum.map(fn x -> x * x end) +|> Enum.filter(fn x -> rem(x, 2) == 0 end) +#=> [4, 16, 36, 64, 100] + ## --------------------------- ## -- Structs and Exceptions ## --------------------------- @@ -338,6 +362,7 @@ rescue RuntimeError -> "rescued a runtime error" _error -> "this will rescue any error" end +#=> "rescued a runtime error" # All exceptions have a message try do @@ -346,6 +371,7 @@ rescue x in [RuntimeError] -> x.message end +#=> "some error" ## --------------------------- ## -- Concurrency @@ -364,6 +390,13 @@ spawn(f) #=> #PID<0.40.0> # messages to the process. To do message passing we use the `send` operator. # For all of this to be useful we need to be able to receive messages. This is # achieved with the `receive` mechanism: + +# The `receive do` block is used to listen for messages and process +# them when they are received. A `receive do` block will only +# process one received message. In order to process multiple +# messages, a function with a `receive do` block must recursively +# call itself to get into the `receive do` block again. + defmodule Geometry do def area_loop do receive do @@ -379,6 +412,8 @@ end # Compile the module and create a process that evaluates `area_loop` in the shell pid = spawn(fn -> Geometry.area_loop() end) #=> #PID<0.40.0> +# Alternatively +pid = spawn(Geometry, :area_loop, []) # Send a message to `pid` that will match a pattern in the receive statement send pid, {:rectangle, 2, 3} @@ -391,11 +426,28 @@ send pid, {:circle, 2} # The shell is also a process, you can use `self` to get the current pid self() #=> #PID<0.27.0> + +## --------------------------- +## -- Agents +## --------------------------- + +# An agent is a process that keeps track of some changing value + +# Create an agent with `Agent.start_link`, passing in a function +# The initial state of the agent will be whatever that function returns +{ok, my_agent} = Agent.start_link(fn -> ["red", "green"] end) + +# `Agent.get` takes an agent name and a `fn` that gets passed the current state +# Whatever that `fn` returns is what you'll get back +Agent.get(my_agent, fn colors -> colors end) #=> ["red", "green"] + +# Update the agent's state the same way +Agent.update(my_agent, fn colors -> ["blue" | colors] end) ``` ## References -* [Getting started guide](http://elixir-lang.org/getting_started/1.html) from [elixir webpage](http://elixir-lang.org) +* [Getting started guide](http://elixir-lang.org/getting-started/introduction.html) from the [Elixir website](http://elixir-lang.org) * [Elixir Documentation](http://elixir-lang.org/docs/master/) * ["Programming Elixir"](https://pragprog.com/book/elixir/programming-elixir) by Dave Thomas * [Elixir Cheat Sheet](http://media.pragprog.com/titles/elixir/ElixirCheat.pdf) |