Changes between Version 7 and Version 8 of Ticket #31725


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Timestamp:
Apr 25, 2021, 5:16:59 AM (18 months ago)
Author:
Yuan Zhou
Comment:

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  • Ticket #31725 – Description

    v7 v8  
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    10 Currently, `FinitePoset._hasse_diagram` has `@lazy_attribute _meet` (resp. `_join`) and method `meet_matrix` (resp. `join_matrix`). However, they don't compute the matrix but raise an Error if the poset is not a meet/join-semilattice or if there is a pair of x and y whose meet doesn't exist.
     10Currently, `FinitePoset._hasse_diagram` has `@lazy_attribute _meet` (resp. `_join`) and method `meet_matrix` (resp. `join_matrix`). However, they don't compute the matrix but raise an Error if the poset is not a meet/join-semilattice.
    1111
    1212We propose to change `HasseDiagram._meet` (resp. `_join`) and `HasseDiagram.meet_matrix()` (resp. `join_matrix`), so that the `(x,y)`-entry of the matrix is `None` if the meet of `x` and `y` doesn't exist, instead of raising an Error. Then, we make the method `FinitePoset.meet(x, y)` (resp. `join(x, y)`) by applying the `_element_to_vertex` and `_vertex_to_element` conversions on `poset._hasse_diagram._meet[x, y]`.