Re: [Maxima-discuss] ((MPLUS SIMP FACTORED) 2 3) -> 3 + 2

[Stavros M. <mac...@gm...>]

Good point.

The documentation for *powerdisp* is incomplete/misleading. It reads:

     When ‘powerdisp’ is ‘true’, a sum is displayed with its terms in
     order of increasing power.

But as you say, it actually reverses *all* the terms, not just the powers:

apply('matrix,makelist( [ string(ex), block([powerdisp:true],string(ex))],
ex, [x+y, a+b, x^3+y^2+z, z^3+y^2+x, z^2+x^2]));
      [    y+x        x+y    ]
      [                      ]
      [    b+a        a+b    ]
      [                      ]
      [ z+y^2+x^3  x^3+y^2+z ]
      [                      ]
      [ z^3+y^2+x  x+y^2+z^3 ]
      [                      ]
      [  z^2+x^2    x^2+z^2  ]



On Tue, Oct 29, 2024 at 1:28 PM Robert Dodier <rob...@gm...>
wrote:

> On Tue, Oct 29, 2024 at 8:33 AM Stavros Macrakis <mac...@gm...>
> wrote:
>
> > Using great ordering for displaying products and reversed great ordering
> for sums is, as I said, "a crude heuristic, but it produces pretty good
> results". To improve on that, great should not be modified -- that should
> be done in nformat, which already does things like
> a*b^-1*c*q^-1*w*x^-1*y*z^-1 (internal format) => (a*c*w*y)/(b*q*x*z)
> (external format), rat(2,3)*x => (2*x)/3, x^rat(-1,2) => 1/sqrt(x), etc.
> >
> > Maybe you could start by making a list of cases where you think Maxima
> is producing suboptimal display orderings. Keep in mind that the ordering
> often depends on what is considered a "variable" and what is considered a
> "parameter".
>
> I haven't been following closely, but anyway see also the global flag
> powerdisp which governs whether "+" expressions are displayed with
> terms as ordered by GREAT, or in the opposite order. I forget which is
> the default.
>
> HTH
>
> Robert
>