Task

Write a boolean function that tells whether a given integer is prime.



Remember that   1   and all non-positive numbers are not prime.

Use trial division.

Even numbers greater than   2   may be eliminated right away.

A loop from   3   to   √ n    will suffice,   but other loops are allowed.



Related tasks

   count in factors
   prime decomposition
   AKS test for primes
   factors of an integer
   Sieve of Eratosthenes
   factors of a Mersenne number
   trial factoring of a Mersenne number
   partition an integer X into N primes
   sequence of primes by Trial Division


defmodule RC do
  def is_prime(2), do: true
  def is_prime(n) when n<2 or rem(n,2)==0, do: false
  def is_prime(n), do: is_prime(n,3)
 
  def is_prime(n,k) when n<k*k, do: true
  def is_prime(n,k) when rem(n,k)==0, do: false
  def is_prime(n,k), do: is_prime(n,k+2)
end
 
IO.inspect for n <- 1..50, RC.is_prime(n), do: n