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When writing Elixir functions, we can make use of an assertive style with pattern matching:

def read_file() do
  {:ok, contents} = File.read("hello.txt")
  contents
end

Pattern matching is explicitly performed using the match operator, =/2.
- Matches succeed when the shape of the data on the left side of the operator matches the right side.
- When matches succeed, variables on the left are bound to the values on the right.
- Using an underscore, _, allows us to disregard the values in those places.
```
{:ok, number, _} = {:ok, 5, [4.5, 6.3]}
number
# => 5 is bound to this variable
```
- The pin operator ^ can be used to prevent rebounding a variable and instead pattern match against its existing value.
```
number = 10
{:ok, ^number, _} = {:ok, 5, [4.5, 6.3]}
# => ** (MatchError) no match of right hand side value: {:ok, 5, [4.5, 6.3]}
```
Pattern matches may also occur in a function clause head, so that only arguments that match the pattern will invoke the function.

Variables can be bound in a function clause pattern match.

defmodule Example do
  def named_function(:a = atom_variable) do
    {atom_variable, 1}
  end
end

Example.named_function(:a)
# => {:a, 1}
# The first function clause matches, so it is invoked

Example.named_function(:b)
# => ** (FunctionClauseError) no function clause matching in Example.named_function/1

Originally from Exercism elixir concepts

Pattern Matching

Lesson Overview

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