Add to_digraph method to Permutation

[slel]

Before this ticket, the show method for a permutation

• computes a graph corresponding to that permutation
• displays it
• but does not return it

This ticket adds a to_digraph method to return the graph
and changes the show method to use it.

This allows the following:

sage: p = Permutation([3, 1, 2])
sage: g = p.to_digraph()
sage: g.edges(labels=False)
[(1, 3), (2, 1), (3, 2)]

Inspired by a question by Ask Sage user magviana:

• Ask Sage question 52649: How to LaTeX the graph of a permutation?

CC: @slel

Component: combinatorics

Keywords: permutation

Author: David Coudert

Branch/Commit: 12cadec

Reviewer: Sébastien Labbé

Issue created by migration from https://trac.sagemath.org/ticket/30214

[dcoudert]

Author: David Coudert

[dcoudert]

comment:1

This should do what you want.

---

New commits:

498f093

trac #30214: add method to_digraph to Permutation

[dcoudert]

Commit: 498f093

[dcoudert]

Branch: public/combinat/30214_to_digraph

[seblabbe]

comment:3

Personally, I would do

-E = [(i + 1, self[i]) for i in range(len(self))]
+E = list(enumerate(self, start=1)))

Do you agree?

[seblabbe]

Reviewer: Sébastien Labbé

[slel]

comment:5

Replying to @seblabbe:

Personally, I would do

-E = [(i + 1, self[i]) for i in range(len(self))]
+E = list(enumerate(self, start=1)))

Do you agree?

+1

[sagetrac-git]

Changed commit from 498f093 to 12cadec

[sagetrac-git]

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

08c3e05	trac #30214: merged with 9.2.beta8
12cadec	trac #30214: use enumerate and avoid creation of list

[dcoudert]

comment:7

Indeed a better solution. I'm also avoiding the creation of the list.

[seblabbe]

comment:8

good, I was not sure if it takes an iterable as well. even better.

[dcoudert]

comment:9

When the input format is specified, you can give an iterator. Otherwise...

[vbraun]

Changed branch from public/combinat/30214_to_digraph to 12cadec