class Prime

Public Instance Methods

factors(n,primes) click to toggle source
# File lib/prime.rb, line 2
def factors(n,primes)
        is_prime = true
        n_sqrt = Math.sqrt(n).ceil
        selected_primes = primes.select {|num| num<=n_sqrt }
        selected_primes.each {|x|
                (is_prime=false; break) if n%x==0
        }
        is_prime
end
get_nth_prime(n) click to toggle source
# File lib/prime.rb, line 11
def get_nth_prime(n)
        prime_ary = []
        first_digit = 1
        next_digit = first_digit + 1
        while (prime_ary.length < n) do
                (prime_ary << next_digit) if factors(next_digit,prime_ary)
                next_digit.even? ? next_digit += 1 : next_digit += 2                 
        end
        p "Your #{n}th Prime Number is : #{prime_ary.last}"
        prime_ary.last
end