LaTeX representation of negative symbolic fractions broken

[nexttime]

When the numerator of a (negative) symbolic expression happens to be 1 (and only then), the sign is dropped in its LaTeX representation (but not its string representation):

sage: latex(-1/x) 
\frac{1}{x}
sage: latex(1/-x) 
\frac{1}{x}

Origin of the new doctest failure in sage/graphs/generic_graphy.py, introduced with Sage 4.4.3.alpha0.

---

Update:

Actually, though I tested many other cases, the same (still) happens if both the numerator and denominator are (symbolic) variables (see also #9086 comment:12):

sage: var("x y")
(x, y)
sage: latex(-x/y)
\frac{x}{y}
sage: latex(x/-y)
\frac{x}{y}

But since it was discovered after the patch that fixes the first issue had been merged, the latter bug is now #9314.

Component: symbolics

Keywords: symbolic fraction, sign, minus, latex, pynac

Author: William Stein

Reviewer: Mike Hansen

Merged: sage-4.4.3.alpha2

Issue created by migration from https://trac.sagemath.org/ticket/9086

[burcin]

Changed keywords from symbolic fraction, sign, minus, latex to symbolic fraction, sign, minus, latex, pynac

[burcin]

comment:1

Thanks for tracking this down. This patch is the culprit:

http://pynac.sagemath.org/hg/rev/cbd65a7dcf6a

I will only be able to look at this after next weekend.

[williamstein]

Attachment: trac_9086.patch.gz

apply to sage library

[williamstein]

Attachment: trac_9086-apply_to_pynac.patch.gz

apply to src/ repo in pynac spkg

[williamstein]

comment:2

The patch to the pynac spkg is long, but is logically nearly trivial. I just copied some code for printing a sign, which Burcin forgot.

The patch to the sage library is merely to test that this is fixed.

William

[williamstein]

comment:3

New spkg here:

http://sage.math.washington.edu/home/wstein/patches/pynac-0.2.0.p1.spkg

[mwhansen]

comment:4

This looks good to me and fixes the issue. There was a change for #9037 that didn't get included in the spkg merged so far in 4.4.3 so I've included it at

http://sage.math.washington.edu/home/mhansen/pynac-0.2.0.p1.spkg

which should be used instead of the above link.

[mwhansen]

Author: William Stein

[mwhansen]

Reviewer: Mike Hansen

[williamstein]

comment:5

Mike, Can you give #9037 a positive review?

[mwhansen]

comment:6

Positive review up at #9037.

[williamstein]

Merged: 4.4.3.alpha2

[sagetrac-mvngu]

Changed merged from 4.4.3.alpha2 to sage-4.4.3.alpha2

[sagetrac-damm]

comment:12

Replying to @sagetrac-damm:
Sorry, i've changed the description and couldn't revert the change.

I think the fix didn't solve all problems:

sage: var('x y')
sage: latex(-x/y) 
\frac{x}{y}

[nexttime]

comment:13

Replying to @sagetrac-damm:

I think the fix didn't solve all problems

Indeed. Despite the ticket's name, I think this second case should be addressed on another ticket, since this one had already been merged.

[sagetrac-damm]

comment:14

Done. #9314