# File lib/more/facets/math/epsilon.rb, line 7 def self.epsilon(i, j, k) i = Integer(i) return nil if i < 1 or i > 3 j = Integer(j) return nil if j < 1 or j > 3 k = Integer(k) return nil if k < 1 or k > 3 case i * 16 + j * 4 + k when 27, 45, 54 then return 1 when 30, 39, 57 then return -1 end 0 end