Defining Elixir Protocols

protocol.md

#Define a Protocol

A Protocol is a way to dispatch to a particular implementation of a function based on the type of the parameter.
The macros defprotocol and defimpl are used to define Protocols and Protocol implementations for different types in the following example.

defprotocol Triple do    
  def triple(input)  
end  

defimpl Triple, for: Integer do    
  def triple(int) do     
    int * 3   
  end  
end   

defimpl Triple, for: List do
  def triple(list) do
    list ++ list ++ list   
  end  
end 

Usage

Load the code into iex and execute

iex> Triple.triple(3) 
9
Triple.triple([1, 2])
[1, 2, 1, 2,1,2]