Do not allow numbers to be used as variable names
Quoting the report attached from Teams/Design/usability#48 (closed):
Issue no. 2: Calculator fails to recognize numeric variable names during recall, yet allows items to be saved with numbers in the memory function.
I typed the number ”25” into the input field. To save this number, I opened the memory function, inputted a numeric variable name “19”, and clicked the “Store Value…” icon To recall the stored value, I typed the variable name and selected it from the popover that comes up on the display area I added the number “2” to the variable name and got the result “21”.
I expected the result to be “27”, but understood that the system did not recognize 19 as a valid variable name. In that case, I expected to have received some sort of error message stating that numbers cannot be variable names while sorting the value.