def is_prime?(n)
  bits = 8.times.map { |i| n[i] }
  [[[-8.8,  3.0,  9.2,  5.0, -4.8,  5.6, -5.8,  6.1, -6.1],
    [-1.8,  2.3, -2.6, -5.6,  0.1,  6.0, -4.7, -5.7, -3.0],
    [-3.6, -4.1,  6.5, -0.6, -2.8, -2.6,  2.4, -2.3,  1.0],
    [ 2.4, -9.1, -3.1,  7.8, -3.7, -8.9, -2.8,  5.6,  6.3],
    [-2.0,  4.0, 11.0,  3.3, -6.0,  0.7, -7.0,  1.6, -3.0],
    [ 0.7, -7.2,  2.8,  4.5, -3.6, -1.5,  2.7, -0.1, -3.5],
    [-8.9,  5.5,  4.8, -4.1,  5.6,  4.8,  5.5, -4.0, -6.4],
    [-4.0, -6.7, -3.6,  5.5,  2.5, -6.9,  7.8, -4.1, -0.4],
    [ 1.1, -3.5, -6.7, -2.8,  2.3, -4.7,  6.3, -4.6, -2.2]
   ],
   [[-14.6, -13.9, -9.4, -10.8, 13.7, 10.6, -10.7, -11.0, 12.7,  5.2]],
  ]
  .inject(bits) { |nodes_lhs, synapseses_rhs_major|
    synapseses_rhs_major.map { |synapses|
      total_input = [*nodes_lhs, 1.0].zip(synapses).map { |n, s| n*s }.inject(0, :+)
      1 / (1 + Math::E ** -total_input) # https://en.wikipedia.org/wiki/Sigmoid_function
    }
  }.first > 0.5
end

require 'prime'
(256).times.all? { |n| is_prime?(n) == Prime.prime?(n) } # => true