more practical construction of word paths

[seblabbe]

Improve the construction of word path parent : creation from 2*n letters and n vectors now works (it takes the opposite of vectors).

CC: @sagetrac-abmasse

Component: combinatorics

Author: Sébastien Labbé

Reviewer: Alexandre Blondin Massé, Nathann Cohen

Merged: sage-4.4.1.alpha2

Issue created by migration from https://trac.sagemath.org/ticket/8407

[sagetrac-abmasse]

comment:2

These functions are really interesting ! I can't wait to use them. However, here are some comments:

1. I think this patch is a good occasion to add functions such as rotate() and reflects() (with pertinent parameters) that compute ONE rotated or reflected version of the path instead of all EIGHT at the same time. This wouldn't be too long to do and then your function isometries() could call them.

2. I don't understand why you use the parameter reversal. If I understand it well, it is the word reversal operator, which can be geometrically interpreted as performing a rotation of angle pi (of the path) together with an orientation reversal of the path. It seems more natural to me that the parameter reversal correspond simply to the orientation reversal rather than to the word reversal.

3. I noticed that you do not use the word "self" while documenting, but you use "path" or other similar words. I'm not sure which one is a good practice, but I think it is better to use the first one (I'm really not sure about it, so maybe you can correct me).

What do you think ?

[sagetrac-abmasse]

comment:3

Just noticed I should have set this ticket to "needs work". Done.

[seblabbe]

Description changed:

--- 
+++ 
@@ -1,3 +1 @@
-1. Add a function that returns the isometries of word paths on the square grid.
-
-2. Improve the construction of word path parent : creation from 2*n letters and n vectors now works (it takes the opposite of vectors).
+Improve the construction of word path parent : creation from 2*n letters and n vectors now works (it takes the opposite of vectors).

[seblabbe]

comment:4

I removed one of the objectives of the ticket related to isometries. Indeed, I need this function for another problem so I think its use will be more understood in context. So that is why I removed this part from this ticket. I will create a new ticket for it soon.

[seblabbe]

Attachment: trac_8407_word-paths-sl.patch.gz