Hi John,
> Are you saying it is possible or that it *should* be possible to use
> pointer-to-static-member-function?
For sure it is possible, I did it a lot of times. There is no any difference
between C-function and static function of a class.
For instance such approach I used it TThread class.
> Either it is not possible or the syntax is tricky indeed!
sintax no more tricky than all busyness with the pointers to C++ functions
Victor
Victor M. Perevoztchikov perev@bnl.gov
Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000
tel office : 631-344-7894; fax 631-344-4206;
----- Original Message -----
From: "Dr. John Krane" <jkrane@netzero.com>
To: "Victor Perevoztchikov" <perev@bnl.gov>
Cc: "Rene Brun" <Rene.Brun@cern.ch>; <roottalk@pcroot.cern.ch>
Sent: Tuesday, July 22, 2003 1:24 PM
Subject: Re: [ROOT] fitting with a member function
> Hi Victor,
>
> Are you saying it is possible or that it *should* be possible to use
> pointer-to-static-member-function? I played around with pointers to
> static member functions for quite some time before writing to Roottalk.
> Either it is not possible or the syntax is tricky indeed!
>
> If it is not currently possible to just use a pointer I will continue
> with Philippe's proposed solution. My Root v3.05/06 is building right
> now...
>
> - John
>
> Victor Perevoztchikov wrote:
> > Hi Rene,
> > just remark,
> >
> >>// This also apply to the case of a static class function.
> >
> > You can use static function of class. There is no difference in
> > C-function and static function of a class. The pointer to function is
the
> > same.
> > It is used for example in TThread
> >
> >
> > Also, I think , it would be good to allow do the fit with the special
class.
> > Let say
> > class THFun { public: virtual Fcn(...)=0;}
> > Then user can create his own class inherited from THFun and overload
Fcn.
> > and provide the pointer of the object to TH1 class
> >
> > It is more flexible than just user function, because user can have some
non
> > global
> > variables, to communicate, some additional methods etc....
> > The same for TMinuit.
> >
> > Victor
> >
> >
> > Victor M. Perevoztchikov perev@bnl.gov
> > Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000
> > tel office : 631-344-7894; fax 631-344-4206;
> >
> > ----- Original Message -----
> > From: "Rene Brun" <Rene.Brun@cern.ch>
> > To: "Dr. John Krane" <jkrane@netzero.com>
> > Cc: <roottalk@pcroot.cern.ch>
> > Sent: Tuesday, July 22, 2003 12:31 PM
> > Subject: Re: [ROOT] fitting with a member function
> >
> >
> >
> >>Hi John,
> >>
> >>The TF1 doc has this remark:
> >>
> >>//
> >>// WHY TF1 CANNOT ACCEPT A CLASS MEMBER FUNCTION ?
> >>// ===============================================
> >>// This is a frequently asked question.
> >>// C++ is a strongly typed language. There is no way for TF1 (without
> >>// recompiling this class) to know about all possible user defined data
> >
> > types.
> >
> >>// This also apply to the case of a static class function.
> >>
> >>
> >>In the C-style function referenced by TF1 and called from TH1::Fit,
> >>you can call your class member function.
> >>You can either use a global to access an object of your class
> >>or use TVirtualFitter::SetUserFunc to register the address of a TObject*
> >>to the fitter. In the C-style function, you can retrieve this pointer
> >>with something like:
> >> TObject *myobject = TVirtualfitter::GetFitter()->GetUserFunc();
> >>
> >>Rene Brun
> >>
> >>
> >>"Dr. John Krane" wrote:
> >>
> >>>Hi,
> >>>
> >>>I'm trying to use weighted histograms to fit a distribution. Because I
> >>>want to be able to change the histos that I'm using as components, I
> >>>made a little class that holds an array of TH1F. A member function
> >>>provides the weighted sum of these histograms, with the weights being
> >>>the fit parameters and the interface being as required by TF1. So I
> >>>tried to make a TF1 for use with the ->Fit method, like this:
> >>>
> >>> cerr<< "Assign the histos that contribute to fit"<<endl;
> >>> func_fit fclass;
> >>> fclass.add_param(d1or); file://first histo
> >>> fclass.add_param(d1crl); file://second histo...etc.
> >>>
> >>> TF1 *fitFcn = new
> >>> TF1("fitFcn",fclass.func_val,-600.,-1.,fclass.get_nparam());
> >>>
> >>>Well the compiler within ROOT doesn't like that, so I tried making a
> >>>pointer-to-member-function and giving that to root, but I didn't get
> >>>anywhere. Does anybody know how to provide a member-function to TF1?
I
> >>>think my class solution is quite clean for what I'd like to do, but I
> >>>need to get around this barrier...
> >>>
> >>> - John
> >>
> >
> >
> >
>
>
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