Higher Level Types

All the build-in types discussed in previous blog posts are inherited by Erlang Type system. But on top of these types Elixir provides some higher-level abstraction.

Now the Elixir magic is coming, the most frequent are Range, Keyword, MapSet ,Date, Time, NaiveDateTime and DateTime.

Range

A range is an abstraction that allows you to represent a range of numbers. The syntax is i..j.

iex(1)> my_range = 1..2
1..2
iex(2)> 1 in my_range
true
iex(3)> 100 in my_range
false
iex(4)>

Use of in operator ^^

Range is enumerable, so we can use range on function from Enum modules, like

defmodule Main do
 
  def main do
 
    Enum.each(1..10, &IO.puts/1)
 
  end
 
end
 
Main.main

range is just implemented by a Map, which means it just store the starting and the finish value, hence range is very efficient for any range values.

Keyword List

Keyword list is an abstraction over normal list (yes... the complexity of keyword list is also O(N)). A keyword list is essentially a list of tuples containing two elements, first is an atom and second can be anything.

iex(2)> kw_list = [{:debug, true}, {:port, "8080"}, {:env, "dev"}]
[debug: true, port: "8080", env: "dev"]
iex(3)>

To make the syntax of Keyword List more elegant, we can omit {} and put : after the atom name, just like in Objects

iex(3)> kw_list = [debug: true, port: "8080", env: "dev"]
[debug: true, port: "8080", env: "dev"]
iex(4)>

There are many available function in Keyword module check: https://hexdocs.pm/elixir/Keyword.htm

Keyword list is heavily used in Elixir and Erlang for optional arguments, we use keyword list a last parameter so clients can give any amount of option arguments.

defmodule Main do
 
  def main do
 
    printer(0, 2)
    printer(0, 2, [msg: "Hello"])
    printer(0, 2, msg: "Hello", msg_2: "World")
  end
 
  def printer(i, j, options \\ []) do
 
    msg = Keyword.get(options, :msg, "")
    msg2 = Keyword.get(options, :msg_2, "")
 
    Enum.each(i..j, fn x ->
      IO.puts(msg)
      IO.puts(x)
      IO.puts(msg2)
    end)
 
 
  end
 
end
 
Main.main

Line 5. We are not giving any optional arguments, 6. use are using keyword list syntax to pass one option arguments 7. Since this Pattern is so common we can omit []

This is the best use case of _Keyword List _ in Elixir and Erlang world.

MapSet

It is just SET!

iex(4)> set = MapSet.new([1, 2, 2, 3, 2, 1, 1])
MapSet.new([1, 2, 3])
iex(5)>

We use MapSet module to work with Sets and you can find more API reference about MapSet here: https://hexdocs.pm/elixir/MapSet.html.

iex(4)> set = MapSet.new([1, 2, 2, 3, 2, 1, 1])
MapSet.new([1, 2, 3])
iex(5)> MapSet.member?(set, 2)
true
iex(6)> MapSet.member?(set, 99)
false
iex(7)> set = MapSet.put(set, 100)
MapSet.new([1, 2, 3, 100])
iex(8)>

Dates & Time

https://hexdocs.pm/elixir/Date.html

https://hexdocs.pm/elixir/Time.html

https://hexdocs.pm/elixir/DateTime.html

https://hexdocs.pm/elixir/NaiveDateTime.html