Re: [Maxima-discuss] Weird behaviour of maxima and tex function with minus signs

[Robert D. <rob...@gm...>]

On Fri, Oct 17, 2025 at 11:54 AM LÓPEZ MEDINA, DAVID JAVIER
<Dav...@up...> wrote:

> (%i1) -1-2*x-(-3*y)-4*z;
>
> leads to the output
>
> (%o1) - 4 z + 3 y - 2 x - 1
>
> (what is nice), but the tex output is strange
>
> (%i2) tex(%)$
> $$-\left(4\,z\right)+3\,y-2\,x-1$$

Placement of parentheses is governed by what is called right binding
power and left binding power -- these are essentially operator
precedence levels. The rbp and lbp for various operators have been
adjusted over the years to solve parentheses placement problems, in
particular, to ensure that there are parentheses to make the
expression unambiguous. This sometimes leads to excess parentheses, as
we see here.

A quick fix for this specific problem is

:lisp (setf (get 'mminus 'tex-rbp) 100)

which, for TeX output, reduces the right binding power from its
current value (134) to 100. This is enough to get the expected
behavior in the example shown -- after that, I get

tex (-1-2*x-(-3*y)-4*z);
 => $$-4\,z+3\,y-2\,x-1$$

Whether the different binding power is generally desirable would
depend on how it interacts with other operators such as "+", "*", "/",
and "^". I will open a bug report about to keep track of whatever I
(or anyone else) can figure out.

Robert