bug in conversion powers in to LaTeX

[robert-marik]

The LaTeX representation of (x^pi)e is not valid TeX string and is not rendered by jsmath

sage: latex((x^pi)^e)
{(x)}^{\pi}^{e}

Burcin suggested how to fix this and get output like

{{(x)}^{\pi}}^{e}

The code for printing
symbolic expressions is in pynac (C++). The fix can be as simple as
printing an extra set of braces around power objects.

If anybody wants to try fixing this, the relevant function is
power::do_print_latex() in power.cpp. To get to the file (using the
instructions I wrote in another message just now), go to your SAGE_ROOT
and do:

./sage -f -s spkg/standard/pynac-0.1.9.p0.spkg

cd spkg/build/pynac-0.1.9/src/ginac

Edit power.cpp. To compile and make your changes effective, go to your
SAGE_ROOT again, and do

./sage -sh
cd spkg/build/pynac-0.1.9/src
make install 

However a better fix would be to get

{x}^{a}

if the base is an atom (or not power) and

\left({x^a}\right)^{b}

if the base is a power. This allows to distinguish easily between

x^(a^b) 

and

(x^a)^b

A workaround is to remove powers of powers by simplification. For example radcan function from Maxima perfoms such simplifications

sage: latex(maxima((x^pi)^e).radcan().sage())
x^{\pi e}

Component: symbolics

Keywords: latex, power, jsmath, pynac

Author: Burcin Erocal

Reviewer: Karl-Dieter Crisman

Merged: sage-4.3.rc0

Issue created by migration from https://trac.sagemath.org/ticket/7406

[robert-marik]

Changed keywords from latex, power, jsmath to latex, power, jsmath, pynac

[robert-marik]

comment:3

Perhaps close problem is

sage: latex(x*(1/(x^2)+sqrt(x^7)))
{(\sqrt{x^{7}} + \frac{1}{x^{2}})} x

Note missing \left and \right at outside parentheses which makes the rendering of the expression far from perfect. Should look like

sage: latex(x*(1/(x^2)+sqrt(x^7)))
{\left(\sqrt{x^{7}} + \frac{1}{x^{2}}\right)} x

[burcin]

add doctests

[burcin]

comment:4

Attachment: trac_7406-power_latex.patch.gz

The new pynac package here

http://sage.math.washington.edu/home/burcin/pynac/pynac-0.1.10.spkg

contains fixes for both the problem in the description and the one in comment:3.

attachment: trac_7406-power_latex.patch contains doctests for the fix.

Note that the new pynac version also contains fixes for #7508 and #7264. Tests should be run with the patches from those tickets also applied in this order:

• hash collisions for derivatives of symbolic functions - act 3 #7508
• segfault while substituting powers of exp #7264
• bug in conversion powers in to LaTeX #7406 (this ticket)

This ticket now depends on #7490, #7508 and #7264.

[burcin]

Author: Burcin Erocal

[kcrisman]

comment:5

Positive review - they look great in show()! Obviously pending #7264 or a rebase.

[mwhansen]

Reviewer: Karl-Dieter Crisman

[mwhansen]

Merged: sage-4.3.rc0