Knot theory: Change PD-code convention

[seb....@gmail.com]

Hi everybody,

The PD (Planar Diagram) notation is one of the most important concepts to define a knot or link uniquely (besides the braid notation). Unfortunately our convention on how to read the four strands meeting at a crossing is opposite to the one used in most other places: We read them in clockwise direction whereas most others do it anti-clockwise.

I've started a discussion in issue #17030 (the ticket that introduced knot theory in Sage in 2014) to change our convention accordingly (starting from this comment).

If you have objections to this, please comment there!

Sebastian

[seb....@gmail.com]

PR #35665 implementing the convention change is now available for review.