chapter6-pattern-matching.exs

defmodule Math do
    # Implement and run a function sum(n) that uses recursion to calculate
    # the sum of the integers from 1 to n. You’ll need to write this function
    # inside a module in a separate file. Then load up IEx, compile that file,
    # and try your function.
    def sum(0), do: 0
    def sum(n), do: n + sum(n - 1)

    # Write a function gcd(x,y) that finds the greatest common divisor
    # between two nonnegative integers.
    # Algebraically, gcd(x,y) is x if y is zero; it’s gcd(y, rem(x,y)) otherwise.
    def gcd(x, 0), do: x
    def gcd(x, y), do: gcd(y, rem(x, y))
end