10 #ifndef ROOT_Minuit2_GradientCalculator 
   11 #define ROOT_Minuit2_GradientCalculator 
   18 class MinimumParameters;
 
   19 class FunctionGradient;
 
   25 class GradientCalculator {
 
   29   virtual ~GradientCalculator() {}
 
   31   virtual FunctionGradient operator()(
const MinimumParameters&) 
const = 0;
 
   33   virtual FunctionGradient operator()(
const MinimumParameters&,
 
   34                                       const FunctionGradient&) 
const = 0;
 
   41 #endif  // ROOT_Minuit2_GradientCalculator