a new bug in mactex.lisp



> No, they are not! The correct result is
> A^{-(B+C)}
> The result produced by the current code is
> A^{-B+C}
> and it is mathematically incorrect!

OK, I must be missing something here.
Help me understand what's going on.

TeX typesets A^{-B + C} and A^{(-B + C)} as something resembling

  -B + C
A

and

  (-B + C)
A

respectively.
Aren't these two expressions equivalent?
What is an interpretation of A^{-B + C}, other than A^{(-B + C)} ??
Surely A^{-B + C} can't be interpreted as A^{-B} + C,
because that is rendered as

  -B
A    + C

and neither A^-B + C which is rendered as

  -
A B + C

best,
Robert