Revision history [back]

Is it possible that you previously evaluated a command defining var as a string? For example,

var = 'x1'

If you did that (and even if you erased that line), then the line

x1 = var('x1'); x1

would produce the exact error that you are seeing.

Try restarting the worksheet (using the orange "Restart" button at the top), this will reset all names, and now the code should execute as expected.