[ROOT] how to run TVirtualFitter from a c++ class?

From: Christian Hansen (christian.hansen@cern.ch)
Date: Fri Jul 09 2004 - 19:08:01 MEST

> see example in  $ROOTSYS/test/minexam.cxx
> Rene Brun

Hi Rene,

thank you very much for the help! But I'm afraid it did not
give me enough hints since minexam.cxx is no class. In the
attached tar file I have a class called MinuitTest (.C and .h),
where the function to be minimized with TVirtualFitter, 'fcn',
is defined as a member function of the class. But the line


does not go through the compiler, it says:

	MinuitTest.C:14: no matching function for call to 
	`TVirtualFitter::SetFCN(<unknown type>)'

even though I have defined fcn() in MinuitTest.h as 

  void fcn(Int_t &npar, Double_t *gin, Double_t &f, Double_t *par, Int_t iflag);

Why does this not work and how should I do instead? 
(I have tried many different ways, 
 but without success.)

With best regards

> On Fri, 9 Jul 2004, Christian 
> Hansen wrote:
> > 
> > Dear Rooters,
> > 
> > I'm trying to call TMinuit from a c++ class in a similar way
> > that I've used TMinuit in a program called directly from 
> > ROOT, but now I do not  know how to define the 'fcn' 
> > function in order for TMinuit to recognice it with the 
> > 	SetFCN(fcn)
> > I've tried many different ways (attached is a small example)
> > but my code does not want to compile. Could anyone help me how 
> > to change this so that the attached code goes through the compilation?
> > 
> > Thanks!!!
> > 

/ Christian Hansen
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