added a new clear method to clear all vertices, edges, left and right sets

[Krishnadubey1008]

This PR fixes #39756
Added a new clear() method in the BipartiteGraph class to clear the left and right sets.

Please review the changes and let me know if any further improvements needed.

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview.

⌛ Dependencies

[dcoudert]

This fixes the issue. Thanks.

It remains to comply with the coding style:

• add an empty line before the method
• add an empty line after Clear all the vertices and edges in the graph.
• add an EXAMPLES block showing that it's working well. There is no need to repeat all the examples of method clear from generic graph.

[Krishnadubey1008]

@dcoudert I had made the required changes to PR #39760 . Kindly review it!

[dcoudert]

Something like that would be more informative

This method extends the functionality of method :meth:`~sage.graphs.generic_graph.GenericGraph.clear` to also clear vertex sets `left` and `right`.

[dcoudert]

a smaller example like graphs.CycleGraph(4) or even a single edge is sufficient.

[Krishnadubey1008]

@dcoudert I have incorporated the improvements, please tell me if further improvements are needed.

[dcoudert]

ensure that comments are on 80 columns mode and use double ` so ``left``

[Krishnadubey1008]

@dcoudert I had incorporated the changes

[dcoudert]

        This method extends the functionality of method
        :meth:`~sage.graphs.generic_graph.GenericGraph.clear`
        to also clear vertex sets ``left`` and ``right``.

[Krishnadubey1008]

done

[dcoudert]

There is a misunderstanding: I was not asking for removing the one line description of the method. Please restore Clear all the vertices and edges in the graph.

[Krishnadubey1008]

@dcoudert done

[dcoudert]

LGTM.

Tested on my laptop as I cannot launch the CIs.

[user202729]

While this fixes the immediate issue, it doesn't fix the underlying issue. In particular delete_vertices remains broken.

sage: B = BipartiteGraph([(0,2), (0,3), (1,2), (1,3)])
sage: B
Bipartite graph on 4 vertices
sage: B.delete_vertices(B.vertex_iterator())
sage: B
Bipartite graph on 0 vertices
sage: B.left
{0, 1}

The reason is delete_vertices iterates through the input twice, which doesn't deal with iterator input well.

Once delete_vertices is fixed, this newly added method would be redundant. So I don't think it's a particularly good idea to have this in now.

[dcoudert]

If I understand well, you propose to close and forget this PR and open a new one to fix delete_vertices ?

[user202729]

If I understand well, you propose to close and forget this PR and open a new one to fix delete_vertices ?

Yes.

[dcoudert]

@Krishnadubey1008, are you able to do the requested new PR ?

[Krishnadubey1008]

yes, i can try. should I open a new issue or try fix it in this PR itself

[dcoudert]

open a new PR. The issue remains #39756

[Krishnadubey1008]

@dcoudert I had opened a PR #39813 to fix delete_vertices please review.

[dcoudert]

This PR can be closed. A better fix is proposed in #39813.

Thank you @Krishnadubey1008 for the work.

[dcoudert]

@vbraun you can close this PR. A better fix is proposed in #40730. Thank you.