Changes between Version 7 and Version 8 of Ticket #31725
 Timestamp:
 Apr 25, 2021, 5:16:59 AM (18 months ago)
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Ticket #31725 – Description
v7 v8 8 8 9 9 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/joinsemilattice or if there is a pair of x and y whose meet doesn't exist.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/joinsemilattice. 11 11 12 12 We 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]`.