Functional Programming: A PragPub Anthology

Pattern Matching and Functions

Our MyList.sum example shows that pattern matching also applies to calling functions. Do you see that? The function parameters act as the left-hand side of the match, and the arguments you pass act as the right-hand side.

Here is another (hoary old) example: it calculates the value of the n^th Fibonacci number.

Let’s start with the specification of Fibonacci numbers:

fib(0) -> 1
fib(1) -> 1
fib(n) -> fib(n-2) + fib(n-1)

Using pattern matching, we can turn this specification into executable code with minimal effort:

elixir/fib.ex

defmodule Demo do

  def fib(0), do: 1
  def fib(1), do: 1
  def fib(n), do: fib(n-2) + fib(n-1)

end

Elixir comes with an interactive shell called iex. This ...