Bug when using a Convolution in TF1 the second time with a different range #8252
Description
When using the CONV operator in TF1 with a different range, but re-using the same function, the new range is not used correctly.
This code shows the problem:
auto f1 = new TF1("f1","CONV(ROOT::Math::breitwigner_pdf(x,[1],[0]),gaus)",0,10);
f1->SetParameters(5,1,1,0,1);
f1->Draw(); // this is ok
// do convolution in a different range
auto f2 = new TF1("f2","CONV(ROOT::Math::breitwigner_pdf(x,[1],[0]),gaus)",10,20);
f2->SetParameters(15,1,1,0,1);
f2->Draw(); // WRONG result because it performs convolution in 0,10 instead of 10,20
This problem has been reported in https://root-forum.cern.ch/t/fitting-histograms-convolution/44973/7
A simple workaround is just to call:
f2-SetRange(10,20);