anchor.diff:          NOutput:        SizeSpecT
           /// transfer (activation) function
           Info:           Info
  +        /// number of fractional parameters
  +        NFrac:          SizeSpecT
           FracTrainable:  bool
           FracInit:       single
       }
  
positive.code:         let frac =
              if pars.HyperPars.FracTrainable then pars.Frac
              else Expr.assumeZeroDerivative pars.Frac
          let activation = input .* pars.Weights.T + pars.Bias
          Expr.interpolate2D pars.Interpolator (frac *** 2.0f + 0.0001f) activation
  
  
negative.code:         {
              Weights      = mb.Param ("Weights", [hp.NOutput; hp.NInput], initWeights hp)
              Bias         = mb.Param ("Bias",    [hp.NOutput],            initBias hp)
              Frac         = mb.Param ("Frac",    [hp.NFrac],              initFrac hp)
              Interpolator = ip
              HyperPars    = hp
          }
  