Adding height() and width() functions to square grid paths

[sagetrac-abmasse]

When dealing with 2d word paths, it is very useful to know their height and their width.

In particular, one can compute a bounding box for a better displaying. The aim of this small ticket is to add those two functionalities.

By the way, while testing it, I noticed a strange behavior:

sage: Paths = WordPaths('abcABC')
sage: p = Paths('acABC')
sage: points = list(p.points())
sage: points
[(0, 0), (1, 0), (1/2, 1/2*sqrt3), (-1/2, 1/2*sqrt3), (-1, 0), (-1/2, -1/2*sqrt3)]
sage: y_coords = map(lambda (_,y):y, points)
sage: y_coords
[0, 0, 1/2*sqrt3, 1/2*sqrt3, 0, -1/2*sqrt3]
sage: max(y_coords)
-1/2*sqrt3

Shouldn't 1/2*sqrt3 be the highest element ? This doesn't make sense.

CC: @seblabbe @sagetrac-sage-combinat

Component: combinatorics

Keywords: paths, height, width

Author: Alexandre Blondin Massé

Reviewer: Sébastien Labbé

Merged: sage-4.3.4.alpha1

Issue created by migration from https://trac.sagemath.org/ticket/8353

[sagetrac-abmasse]

comment:3

Needs review !

[seblabbe]

comment:6

I would suggest that the value be converted to RR before taking the max or min. You could add a comment explaining the reason of the conversion and that this bug is trac at a ticket number that you give.

The description of this ticket is not really the good place to put your comment. You can put it in a comment of the ticket instead or on sage-devel. I asked the question on sage-devel :
http://groups.google.com/group/sage-devel/browse_thread/thread/2557a48ad695b42e

[sagetrac-abmasse]

comment:7

Thanks for your comments !

I found an almost-clean solution for the problem raised by the triangular grid paths. Instead of computing directly the height() and width() functions, I introduced the xmin(), xmax(), ymin() and ymax() functions we talked about. They are called by the two first functions. To solve the problem for the triangular grid paths, I just redefined them by coercing the x- and y-coordinates to real values, so that the max and min functions be well-defined.

I'll upload another patch in a few minutes. Needs review !

[sagetrac-abmasse]

New patch -- adds functions xmin(), xmax(), etc.

[sagetrac-abmasse]

comment:8

Attachment: trac_8353_square_grid_word_paths_height_width-abm.patch.gz

[seblabbe]

Attachment: trac_8353_review-sl.patch.gz

Applies over the precedent patch

[seblabbe]

Author: Alexandre Blondin Massé

[seblabbe]

comment:9

All tests passed in sage/combinat/words. Documentation builds fine. The issue discussed above is fixed. I am giving a positive review to Alex's changes.

I added a small patch fixing some documentation. If Alexandre agrees with the changes I did, I allow him to change the status of the ticket to positive review.

[seblabbe]

Reviewer: Sébastien Labbé

[sagetrac-abmasse]

comment:10

I agree with Sébastien's changes. I retested it just to make sure, and I looked at the documentation, which is still fine. I'll set this ticket to "positive review".

[mwhansen]

Merged: sage-4.3.4.alpha1