// Sieve of Eratosthenes

n = eval[input["Enter highest number: "]]
results = array[sieve[n]]
println[results]
println[length[results] + " prime numbers less than or equal to " + n]

sieve[n] :=
{
   // Make an array containing the numbers from 0 to n.
   array = array[0 to n]
   array@1 = 0           // Don't consider 1 prime.

   for i = 2 to ceil[sqrt[n]]
      if array@i != 0
         for j = i^2 to n step i
            array@j = 0

   // Return the remaining elements where the element is not zero.
   return select[array, { |x| x != 0 }]
}