Hi, I’m now writing my codes and encountered a really strange error:
As can be seen, the error said "
However, in debugging mode (using Debugger), I can read the value (even add to
So, what’s wrong with it? It’s really confusing …
EDIT: Is there any function to check if a variable is not defined previously?
P.S. Sorry for the images. I don’t know how to paste the result from REPL.