Hi, rand is definitely already defined, it’s the usual C random number generator function,
and it’s always in scope in the ROOT prompt (same as sin, cos and many others).
You will have to choose a more descriptive name for your variable, but this is not necessary a bad thing
Yup. Then we should definitely have a more descriptive name of the TRandom object in $ROOTSYS/tutorials/hist/ as it causes the ROOTbook to fail as I pointed out before.