RealSet, InternalRealInterval: Improve _repr_ and add _latex_ method

[mkoeppe]

We implement this TODO item in RealSet._repr_:

# Switch to u'\u222A' (cup sign) with Python 3

We also add _latex_ methods to RealSet and InternalRealInterval,
upstreaming and extending the change in mkoeppe/cutgeneratingfunctionology@4c7fb7d#diff-b4cd72590a22494dab392e336268a3c94ea5b0adeb6b5864bda0e2ad87c65323

CC: @yuan-zhou @mjungmath @tscrim @fchapoton

Component: manifolds

Author: Matthias Koeppe

Branch/Commit: 011f59a

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/31880

[mkoeppe]

Branch: u/mkoeppe/realset__internalrealinterval__add__latex__method

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

69ca854	RealSet._repr_: Use unicode cup sign instead of +
dbdfc06	InternalRealInterval, RealSet: Remove extra whitespace in latex, add documentation

[sagetrac-git]

Commit: dbdfc06

[mkoeppe]

Description changed:

--- 
+++ 
@@ -1,3 +1,10 @@
-Upstreaming https://github.com/mkoeppe/cutgeneratingfunctionology/commit/4c7fb7df9a92cdb2435028c7eb19d186ab4b58ee#diff-b4cd72590a22494dab392e336268a3c94ea5b0adeb6b5864bda0e2ad87c65323
+We implement this TODO item in `RealSet._repr_`:
+
+```
+# Switch to u'\u222A' (cup sign) with Python 3
+```
+
+We also add `_latex_` methods to `RealSet` and `InternalRealInterval`, 
+upstreaming and extending the change in https://github.com/mkoeppe/cutgeneratingfunctionology/commit/4c7fb7df9a92cdb2435028c7eb19d186ab4b58ee#diff-b4cd72590a22494dab392e336268a3c94ea5b0adeb6b5864bda0e2ad87c65323
 
 

[mkoeppe]

Author: Matthias Koeppe

[tscrim]

comment:5

Trivial failures due to change in output:

sage -t --long --random-seed=0 src/sage/functions/piecewise.py  # 4 doctests failed

Once fixed, you can set it to a positive review.

[tscrim]

Reviewer: Travis Scrimshaw

[sagetrac-git]

Changed commit from dbdfc06 to 7f56338

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

7f56338

PiecewiseFunction: Adjust doctests for changed RealSet repr

[mkoeppe]

comment:7

Thanks!

[sagetrac-git]

Changed commit from 7f56338 to 8abdc8b

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1 and set ticket back to needs_review. New commits:

8abdc8b

src/sage/functions/piecewise.py: Add coding header

[mkoeppe]

comment:9

Added the header as requested in #31927 comment:8