# Symbol differentation in Wolfram Programming Lab gives recursion error [closed]

I was experimenting with the Wolfram Programming Lab, but it doesn't seem to be working. I tried running this code in a notebook:

D[x^2, x]


but it gives the error

$RecursionLimit: Recursion depth of 1024 exceeded during evaluation of 2x.  and gives this as the output (the x after the ∂ is subscript): Hold[$UserPre[∂x x^2]]


It offers the button "release hold", but clicking that doesn't solve the problem. I get the same recursion error and slightly different, though still bizarre, output:

Hold[$UserPre[ReleaseHold[Hold[$UserPre[∂x x^2]]]]]


Even just typing 2 * x gives a recursion error. My understanding is that Wolfram Language is designed around symbolic computation, so why isn't this working?

• It sounds like at some point in the past you have probably ran code that is interfering. To test that theory, you could try running a different piece of code like D[xxxx^2, xxxx]. If that works, you’ve probably redefined x somewhere. The quickest way to solve the problem is probably to go to the Evaluation menu and select Restart Session. This should clear any lingering definitions. Feb 4, 2021 at 3:05
• Huh, I didn't think that would be the issue since I created fresh notebooks before and they reproduced the issue, but I tried again now and it worked. I still feel confused about why creating a fresh notebook didn't work before, but thanks for your help :) Feb 4, 2021 at 4:50
• Also, I don't think I ever defined x before, so I'm not sure if that could have caused it. Feb 4, 2021 at 4:51
• Camelid, creating a “fresh notebook” does nothing to change the current session or alter the condition of the kernel. Simply put, if you have defined x previously & then open a new notebook, this x will remained defined because you are still in the same session or using the same kernel. Feb 4, 2021 at 5:03
• I'm going to vote to close this. It was either a user error or a possibly serious bug. If ever you are able to replicate this, please report it along with steps to reproduce (even if it only happens say every so often). Feb 4, 2021 at 15:23