singletonMultiplicative ::
     (AdditiveMonoid a, DecidableZero a)
  => Unit a -> Int -> LeftTransformation a
singletonMultiplicative a nrs_pred
  | nrs_pred >= 0 = singleton a $ V.replicate nrs_pred zero
  | nrs_pred < 0  = error "LeftTransformation.singletonMultiplicative: negative nrs_pred"
singletonMultiplicative ::
     (AdditiveMonoid a, DecidableZero a)
  => Unit a -> Int -> LeftTransformation a
singletonMultiplicative a nrs_pred
  | nrs_pred >= 0 = singleton a $ V.replicate nrs_pred zero
  | nrs_pred < 0  = error "LeftTransformation.singletonMultiplicative: negative nrs_pred"
singletonMultiplicative a nrs_pred
  | nrs_pred >= 0 = singleton a $ V.replicate nrs_pred zero
  | nrs_pred < 0  = error "LeftTransformation.singletonMultiplicative: negative nrs_pred"