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mwunsch/eratosthenes.rb

Created November 4, 2013 17:50
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eratosthenes.rb
def sieve(n)
integers = 2..n
not_primes = (2..Math.sqrt(n).ceil).reduce([]) do |marked, p|
(p**2).step(n, p) {|j| marked << j }
marked
end
integers.to_a - not_primes
end
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