Recently, I posted an answer to this problem.
Here is a copy of my mail to roottalk on 30 April.
Rene Brun
Because this mail is of general interest, I post my answer to roottalk.
The latest versions of CINT, apparently, are confused in case
of a TF1 constructor with an interpreted function.
If TF1 is called only once with a reference to an interpreted function
(in the example below, the function func), the second call to TF1
invokes the wrong constructor.
I have already forwarded this problem to Masa.
There is a very simple solution to circumvent this problem.
You must force the fonction to a "void *". This helps CINT.
So, in your macro below, change the statements:
TF1* myfunc1 = new TF1("myfunc1", func, -90., 90., 2);
TF1* myfunc2 = new TF1("myfunc2", func, -90., 90., 2);
to
TF1* myfunc1 = new TF1("myfunc1", (void*)func, -90., 90., 2);
TF1* myfunc2 = new TF1("myfunc2", (void*)func, -90., 90., 2);
and your macro will work nicely.
Rene Brun
Daniel Barna wrote:
>
> Hi,
> I would like to plot a function with two different parameters on the same
> canvas. I tried the following:
>
> I wrote the C function in a separate file (func.C)
> for simplicity it is now:
>
> Double_t func(Double_t *arg,Double_t *par)
> {
> return arg[0]*par[0];
> }
>
> And now:
>
> gROOT->LoadMacro("func.C");
>
> TF1 f1("f1",func,-1,1,1);
> f1.SetParameter(0,1);
> f1.Draw(); // ok, it works
>
> TF1 f2("f2",func,-1,1,1);
> f2.SetParameter(0,2);
> f2.Draw("same");
>
> *** Break *** segmentation violation
>
> What did I do wrong?
>
> --------------------------------
> something else:
>
> If I want to write multiple statements between { }s, only the first line
> seems to be executed:
>
> int a=0;
> int b=0;
> for(int i=0; i<10; i++) {a++;
> b++; }
>
> now a=10, but b=1 !
> but if I try
>
> int a=0;
> int b=0;
> for(int i=0; i<10; i++) {a++; b++; }
>
> now a=10,b=10.
>
> Thanks
> Daniel
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