Crystalでエラトステネスの篩

crystal_sieve_of_eratosthenes.cr

require "math/math"

def sieve(max : Int32, tmps : Array(Int32), results: Array(Int32)) : Array(Int32)
  tmp = tmps.first
  return (results + tmps) if tmp > Math.sqrt(max).floor
  sieve(max, tmps.select{|c| c % tmp != 0}, results << tmp)
end

def primaries (max : Int32) : Array(Int32)
  sieve(max, (2..max).to_a, [] of Int32)
end

p primaries 100