Sieve of Eratosthenes

# title: Sieve of Eratosthenes
# source: https://rosettacode.org/wiki/Sieve_of_Eratosthenes
# category: Rosetta Code
# difficulty: Intro
# summary: Generate the prime numbers up to fifty with the classic sieve.
# tags: popular, math, primes, arrays
# vibe: 0.2

def sieve(limit)
  flags = []
  value = 0
  while value <= limit
    flags = flags.push(true)
    value = value + 1
  end

  flags[0] = false
  if limit >= 1
    flags[1] = false
  end

  candidate = 2
  while candidate * candidate <= limit
    if flags[candidate]
      composite = candidate * candidate
      while composite <= limit
        flags[composite] = false
        composite = composite + candidate
      end
    end
    candidate = candidate + 1
  end

  primes = []
  value = 2
  while value <= limit
    if flags[value]
      primes = primes.push(value)
    end
    value = value + 1
  end

  primes
end

def run
  primes = sieve(50)
  {
    limit: 50,
    count: primes.length,
    primes: primes
  }
end