Erlang Prime Generator

gistfile1.txt

defmodule M do
  require Integer
  import :math, only: [sqrt: 1]


  def main do
    IO.puts("Generating large primes...")


    IO.puts "Nummer: #{generate_large_number()}"
    IO.puts "Nummer: #{generate_large_number()}"

    check_if_prime(13)

    for n <- 1..1000 do
      spawn(M, :prime_check_and_stdout, [])
    end

  end

  def prime_check_and_stdout() do
    number = generate_large_number()
    if(is_number_odd(number)) do
      is_prime = check_if_prime number
      #IO.puts number
      if is_prime do
        IO.puts("#{number} is prime!!!")
      end
    end
  end

  def generate_large_number do
    Enum.random(999999999..99999999999999999)
  end

  def is_number_below_threshold(number, threshold) do
    number < threshold
  end

  def is_number_odd(number) do
    rem(number, 2) !== 0
  end

  def check_if_prime_using_bruteforce(number, n, upTo) do
    cond do
      rem(number, n) == 0 -> false
      n < upTo -> check_if_prime_using_bruteforce(number, n + 1, upTo)
      n >= upTo -> true
      true -> IO.puts "What? n: #{n}, number: #{number}, upTo: #{upTo}"
    end
  end


  def check_if_prime(number) do
    !is_number_below_threshold(number, 2) && is_number_odd(number) && check_if_prime_using_bruteforce(number, 2, trunc(sqrt number))
  end
end