calculate lim in CAS with only real numbers

[Lukas]

I wanted to calculate lim(sqrt(2-x),x,2) and expected the HP Prime to tell me that it doesn't exist, because while lim(sqrt(2-x),x,2,-1) exists lim(sqrt(2-x),x,2,1) does not exist.

I guess the HP Prime allows complex solutions and that's why it works out? If so, can I change the settings so that I get the behavior that I expected? How? (I unchecked Complex and Use i in the CAS settings, but that doesn't seem to have helped).

[parisse]

You can't, because the first step in limit is substitution because the CAS is designed to perform computations efficiently. There are other commands that can help you, like domain here.