Re: [ROOT] TFormula parameter name parsing

From: Rene Brun (
Date: Tue Oct 12 2004 - 10:33:21 MEST

Hi Roland,

It is not clear to me what you want to achieve.
It looks like what you are requesting is already implemented
in TTreeFormula.

Rene brun

Roland Kuhn wrote:
> Hi!
> I'd like to use TFormula's parsing capabilities in a ROOT application.
> The problem is, that parameters with real names (like "sigma") cannot
> be readily used since they trigger an error 30 (bad numerical
> expression). Going through the formula in a pre-parsing step and
> replacing the names with [0], [1], and so on kind of defeats the
> purpose of this excercise, as I would need to write a parser myself,
> which would have to know about all the special names ("sin", ...).
> Unless someone can suggest a better solution, I would insert some code
> into TFormula::Analyze so that the "error 30" case (after everything
> else has been tried) is replaced by looking through the list of
> parameter names, replacing this token with the appropriate [n] action,
> adding it to the list first if it didn't yet exist. This should
> probably be configurable as it changes the user interface considerably.
> It's the first time I dig so deeply into ROOT, so if you have any help
> to offer, I would kindly accept any suggestions you wanted to make.
> Ciao,
>                                         Roland
> --
> TU Muenchen, Physik-Department E18, James-Franck-Str. 85747 Garching
> Telefon 089/289-12592; Telefax 089/289-12570
> --
> A mouse is a device used to point at
> the xterm you want to type in.
> Kim Alm on a.s.r.
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