class Prime::EratosthenesSieve

Internal use. An implementation of eratosthenes’s sieve

def extend_table 

def extend_table
  lbound = NUMS_PER_TABLE * @tables.length
  ubound = lbound + NUMS_PER_TABLE
  new_table = [FILLED_ENTRY] * ENTRIES_PER_TABLE # which represents primarity in lbound...ubound
  (3..Integer(Math.sqrt(ubound))).step(2) do |p|
j, k = indices(p)
t if @tables[i][j][k].zero?
rt = (lbound.div(p)+1)*p  # least multiple of p which is >= lbound
rt += p if start.even?
art...ubound).step(2*p) do |n|
, j, k = indices(n)
ew_table[j] &= FILLED_ENTRY^(1<<k)

  end
  @tables << new_table.freeze
end

def indices(n)

for an odd number +n+, returns (i, j, k) such that @tables[i][j][k] represents primarity of the number 
def indices(n)
  #   binary digits of n: |0|1|2|3|4|5|6|7|8|9|10|11|....
  #   indices:            |-|    k  |  j  |     i
  # because of NUMS_PER_ENTRY, NUMS_PER_TABLE
  k = (n & 0b00011111) >> 1
  j = (n & 0b11100000) >> 5
  i = n >> 8
  return i, j, k
end

def initialize # :nodoc:

:nodoc: 
def initialize # :nodoc:
  # bitmap for odd prime numbers less than 256.
  # For an arbitrary odd number n, @tables[i][j][k] is
  # * 1 if n is prime,
  # * 0 if n is composite,
  # where i,j,k = indices(n)
  @tables = [[0xcb6e, 0x64b4, 0x129a, 0x816d, 0x4c32, 0x864a, 0x820d, 0x2196].freeze]
end

def next_to(n)

returns the least odd prime number which is greater than +n+. 
def next_to(n)
  n = (n-1).div(2)*2+3 # the next odd number to given n
  table_index, integer_index, bit_index = indices(n)
  loop do
end_table until @tables.length > table_index
 j in integer_index...ENTRIES_PER_TABLE
f !@tables[table_index][j].zero?
 for k in bit_index...BITS_PER_ENTRY
   return NUMS_PER_TABLE*table_index + NUMS_PER_ENTRY*j + 2*k+1 if !@tables[table_index][j][k].zero?
 end
nd
it_index = 0

le_index += 1; integer_index = 0
  end
end