On Tue, 4 Apr 2017, Robin van der veer wrote:
Thanks for your reply.To me the essence of the definition of join and meetsemilattice is about joins/meets existing for ALL pairs, as opposed to some pairs.
As a slow code you can just say something like Matrix([join2(L, a, b) for a in L] for b in L])
As for your code, I think you want to return j.bottom(), not just the first element of j, correct?
Actually it is the same thing, as for any poset P in Sage we have P[0], P[1], ... a linear extension of P.
Either way I'm not sure that this is efficient enough to be workable, but I will try it.
It should be quite easy to make faster one for bigger posets. OTOH Sage is about never very fast compared to C code, when your computation has for-loops. But then, nowadays computers are so fast that even "slow" code is often fast.
-- Jori Mäntysalo
