Disjointness and complements #
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This file defines disjoint, codisjoint, and the is_compl predicate.
Main declarations #
disjoint x y: two elements of a lattice are disjoint if theirinfis the bottom element.codisjoint x y: two elements of a lattice are codisjoint if theirjoinis the top element.is_compl x y: In a bounded lattice, predicate for "xis a complement ofy". Note that in a non distributive lattice, an element can have several complements.complemented_lattice α: Typeclass stating that any element of a lattice has a complement.
Two elements of a lattice are disjoint if their inf is the bottom element. (This generalizes disjoint sets, viewed as members of the subset lattice.)
Note that we define this without reference to ⊓, as this allows us to talk about orders where
the infimum is not unique, or where implementing has_inf would require additional decidable
arguments.
Instances for disjoint
Alias of the forward direction of disjoint_self.
Alias of the forward direction of codisjoint_self.
- disjoint : disjoint x y
- codisjoint : codisjoint x y
Two elements x and y are complements of each other if x ⊔ y = ⊤ and x ⊓ y = ⊥.
Instances for is_compl
An element is complemented if it has a complement.
Equations
- is_complemented a = ∃ (b : α), is_compl a b
- exists_is_compl : ∀ (a : α), is_complemented a
A complemented bounded lattice is one where every element has a (not necessarily unique) complement.
The sublattice of complemented elements.
Equations
- complementeds α = {a // is_complemented a}
Equations
- complementeds.has_coe_t = {coe := subtype.val (λ (a : α), is_complemented a)}
Equations
Equations
- complementeds.has_sup = {sup := λ (a b : complementeds α), ⟨↑a ⊔ ↑b, _⟩}
Equations
- complementeds.has_inf = {inf := λ (a b : complementeds α), ⟨↑a ⊓ ↑b, _⟩}
Equations
- complementeds.distrib_lattice = function.injective.distrib_lattice coe complementeds.distrib_lattice._proof_1 complementeds.coe_sup complementeds.coe_inf