Pattern Marching and Equals Operator

import IEx.Helpers

The = (match) operator

a = 42

42

a

42

a = 42

42

The pin operator

^a = 42

# ^ = pin operator, to match a value

42

Matching Tuples

place = {:austin, :tx}

{:austin, :tx}

place

{:austin, :tx}

# {city, state} = {:austin, :texas}
{city, state} = place

{:austin, :tx}

"#{city}, #{state}"

"austin, tx"

{city, :tn} = place

{city, state, country} = place

Matching List

three = [1, 2, 3]
four = [4, 5, 6, 7]

[4, 5, 6, 7]

[first, second] = three

defmodule MyList do
  def first_and_second([first, second | list]) do
    "#{first} #{second} #{inspect(list)}"
  end
end

{:module, MyList, <<70, 79, 82, 49, 0, 0, 7, ...>>, {:first_and_second, 1}}

MyList.first_and_second(three)

"1 2 [3]"

MyList.first_and_second(four)

"4 5 [6, 7]"