Add Prime Number in Elixir (#6081)

Author: ricardomaps

archive/e/elixir/prime-number.ex

@@ -0,0 +1,25 @@
+defmodule PrimeNumber do
+  @doc """
+  Determines whether `n` is a prime number.
+  """
+  @spec prime?(n :: integer()) :: bool()
+  def prime?(0), do: false
+  def prime?(1), do: false
+
+  def prime?(n) do
+    high = trunc(:math.sqrt(n))
+
+    if high < 2 do
+      true
+    else
+      Enum.all?(2..high, &(rem(n, &1) != 0))
+    end
+  end
+end
+
+with [arg] <- System.argv(),
+     {n, ""} when n >= 0 <- Integer.parse(arg) do
+  IO.puts(if PrimeNumber.prime?(n), do: "prime", else: "composite")
+else
+  _ -> IO.puts("Usage: please input a non-negative integer")
+end