Ruby program / method that prints out all prime numbers until a given maximum.

prime_numbers.rb

def prime_numbers max
    for i in (2..max) do
        for j in (2..i) do
            break if i%j == 0
        end
        p "#{i} is a prime number." if i == j
    end
end

require 'prime'

def first_n_primes n
  # Check for correct input!
  "n must be an integer" unless n.is_a? Integer
  "n must be greater than 0" if n <= 0

  prime = Prime.instance
  prime.first n
end

Cool