Hi Robert,
Your TF1 formula evaluates correctly but you hit the machine precision
for the
specified returned type (Double_t).
If you try "f1.Eval(70)" you get a non zero result.
Look at the type of the returned value, it's "Double_t" for f1 and
"double" for exp(-71)
Stelios.
----- Original Message -----
From: "Robert Vogel" <robert_vogel@msn.com>
To: <Roottalk@pcroot.cern.ch>
Sent: Friday, June 20, 2003 2:45 PM
Subject: [ROOT] TF1 formula evaluates incorrectly
> Running 3.04/02 on Redhat Linux 7.3.
>
> My TF1 formula does not evaluate correctly, while the explicit formula
> using CINT does:
>
> root [0] TF1 f1("myf1","exp(-x)",0,150)
> root [1] f1.Eval(71)
> (Double_t)0.00000000000000000e+00
> root [2] exp(-71)
> (double)1.46248622725123092e-31
> root [3]
>
> Any suggestions?
>
> Robert Vogel
>
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