Julia lets you write `3x` for `3 * x` because it’s unambiguous, since variables may not start with numerals, but `ax` is not `a * x`, because `ax` is a legal id

Julia lets you write `3x` for `3 * x` because it’s unambiguous, since variables may not start with numerals, but `ax` is not `a * x`, because `ax` is a legal identifier.