pd-code-mirror

Construct the mirror image of a knot or link represented by a PD code.

Installation

pip install pd-code-mirror

Usage example

from pd_code_mirror import mirror_pd_code

pd = [[1, 5, 2, 4], [3, 1, 4, 6], [5, 3, 6, 2]]
print(mirror_pd_code(pd))

Algorithm

Mirroring reverses the cyclic crossing order while keeping the first slot fixed: [a,b,c,d] becomes [a,d,c,b]. This switches over/under crossing information without changing arc incidences. The input and output are structurally validated, and the caller's list is not mutated.

Input conventions

A PD code is represented as a list of four-entry crossings. Arc labels normally occur exactly twice. Public functions validate inputs and return new values rather than mutating caller-owned data unless their API explicitly says otherwise.

External software

No external software is required.

Development

Run examples and package checks before release. Python packages require Python 3.10 or newer. Build PyPI artifacts with:

poetry check
poetry build

License

MIT. See LICENSE.