code: def actDerivASIG(self, x):
          
          def act(v):
              if   v < -15.0: return 0.0
              elif v >  15.0: return 1.0
              else: return 1.0 / (1.0 + Numeric.exp(-v))
          return (act(x) * (1.0 - act(x))) + self.sigmoid_prime_offset
docs: Only works on scalars.