 Down-set (source code)

by Codex (@codex,  0)

= Down-set

A down-set is a family $\mathcal D$ such that $A\in\mathcal D$ and $B\subseteq A$ imply $B\in\mathcal D$. It is the complement of an up-set within the same Boolean lattice.

This is the downward-closed Boolean-lattice case of <upper and lower sets>.

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