Theory of complete lattices #
Main definitions #
sSup
andsInf
are the supremum and the infimum of a set;iSup (f : ι → α)
andiInf (f : ι → α)
are indexed supremum and infimum of a function, defined assSup
andsInf
of the range of this function;- class
CompleteLattice
: a bounded lattice such thatsSup s
is always the least upper boundary ofs
andsInf s
is always the greatest lower boundary ofs
; - class
CompleteLinearOrder
: a linear ordered complete lattice.
Naming conventions #
In lemma names,
sSup
is calledsSup
sInf
is calledsInf
⨆ i, s i
is callediSup
⨅ i, s i
is callediInf
⨆ i j, s i j
is callediSup₂
. This is aniSup
inside aniSup
.⨅ i j, s i j
is callediInf₂
. This is aniInf
inside aniInf
.⨆ i ∈ s, t i
is calledbiSup
for "boundediSup
". This is the special case ofiSup₂
wherej : i ∈ s
.⨅ i ∈ s, t i
is calledbiInf
for "boundediInf
". This is the special case ofiInf₂
wherej : i ∈ s
.
Notation #
Indexed supremum.
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Indexed infimum.
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- OrderDual.supSet α = { sSup := sInf }
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- OrderDual.infSet α = { sInf := sSup }
- le : α → α → Prop
- lt : α → α → Prop
- le_refl : ∀ (a : α), a ≤ a
- sSup : Set α → α
Any element of a set is less than the set supremum.
Any upper bound is more than the set supremum.
Note that we rarely use CompleteSemilatticeSup
(in fact, any such object is always a CompleteLattice
, so it's usually best to start there).
Nevertheless it is sometimes a useful intermediate step in constructions.
Instances
- le : α → α → Prop
- lt : α → α → Prop
- le_refl : ∀ (a : α), a ≤ a
- sInf : Set α → α
Any element of a set is more than the set infimum.
Any lower bound is less than the set infimum.
Note that we rarely use CompleteSemilatticeInf
(in fact, any such object is always a CompleteLattice
, so it's usually best to start there).
Nevertheless it is sometimes a useful intermediate step in constructions.
Instances
- sup : α → α → α
- le : α → α → Prop
- lt : α → α → Prop
- le_refl : ∀ (a : α), a ≤ a
- inf : α → α → α
- sSup : Set α → α
Any element of a set is less than the set supremum.
Any upper bound is more than the set supremum.
- sInf : Set α → α
Any element of a set is more than the set infimum.
Any lower bound is less than the set infimum.
- top : α
- bot : α
Any element is less than the top one.
Any element is more than the bottom one.
A complete lattice is a bounded lattice which has suprema and infima for every subset.
Instances
Equations
- CompleteLattice.toBoundedOrder = BoundedOrder.mk
Create a CompleteLattice
from a PartialOrder
and InfSet
that returns the greatest lower bound of a set. Usually this constructor provides
poor definitional equalities. If other fields are known explicitly, they should be
provided; for example, if inf
is known explicitly, construct the CompleteLattice
instance as
instance : CompleteLattice my_T :=
{ inf := better_inf,
le_inf := ...,
inf_le_right := ...,
inf_le_left := ...
-- don't care to fix sup, sSup, bot, top
..completeLatticeOfInf my_T _ }
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Any CompleteSemilatticeInf
is in fact a CompleteLattice
.
Note that this construction has bad definitional properties:
see the doc-string on completeLatticeOfInf
.
Equations
- completeLatticeOfCompleteSemilatticeInf α = completeLatticeOfInf α (_ : ∀ (s : Set α), IsGLB s (sInf s))
Instances For
Create a CompleteLattice
from a PartialOrder
and SupSet
that returns the least upper bound of a set. Usually this constructor provides
poor definitional equalities. If other fields are known explicitly, they should be
provided; for example, if inf
is known explicitly, construct the CompleteLattice
instance as
instance : CompleteLattice my_T :=
{ inf := better_inf,
le_inf := ...,
inf_le_right := ...,
inf_le_left := ...
-- don't care to fix sup, sInf, bot, top
..completeLatticeOfSup my_T _ }
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Any CompleteSemilatticeSup
is in fact a CompleteLattice
.
Note that this construction has bad definitional properties:
see the doc-string on completeLatticeOfSup
.
Equations
- completeLatticeOfCompleteSemilatticeSup α = completeLatticeOfSup α (_ : ∀ (s : Set α), IsLUB s (sSup s))
Instances For
- sup : α → α → α
- le : α → α → Prop
- lt : α → α → Prop
- le_refl : ∀ (a : α), a ≤ a
- inf : α → α → α
- sSup : Set α → α
- sInf : Set α → α
- top : α
- bot : α
A linear order is total.
- decidableLE : DecidableRel fun x x_1 => x ≤ x_1
In a linearly ordered type, we assume the order relations are all decidable.
- decidableEq : DecidableEq α
In a linearly ordered type, we assume the order relations are all decidable.
- decidableLT : DecidableRel fun x x_1 => x < x_1
In a linearly ordered type, we assume the order relations are all decidable.
A complete linear order is a linear order whose lattice structure is complete.
Instances
Equations
- CompleteLinearOrder.toLinearOrder = LinearOrder.mk (_ : ∀ (a b : α), a ≤ b ∨ b ≤ a) CompleteLinearOrder.decidableLE CompleteLinearOrder.decidableEq CompleteLinearOrder.decidableLT
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Introduction rule to prove that b
is the supremum of s
: it suffices to check that b
is larger than all elements of s
, and that this is not the case of any w < b
.
See csSup_eq_of_forall_le_of_forall_lt_exists_gt
for a version in conditionally complete
lattices.
Introduction rule to prove that b
is the infimum of s
: it suffices to check that b
is smaller than all elements of s
, and that this is not the case of any w > b
.
See csInf_eq_of_forall_ge_of_forall_gt_exists_lt
for a version in conditionally complete
lattices.
Introduction rule to prove that b
is the supremum of f
: it suffices to check that b
is larger than f i
for all i
, and that this is not the case of any w.
See
ciSup_eq_of_forall_le_of_forall_lt_exists_gt
for a version in conditionally complete
lattices.
Introduction rule to prove that b
is the infimum of f
: it suffices to check that b
is smaller than f i
for all i
, and that this is not the case of any w>b
.
See ciInf_eq_of_forall_ge_of_forall_gt_exists_lt
for a version in conditionally complete
lattices.
A version of iSup_option
useful for rewriting right-to-left.
A version of iInf_option
useful for rewriting right-to-left.
When taking the supremum of f : ι → α
, the elements of ι
on which f
gives ⊥
can be
dropped, without changing the result.
When taking the infimum of f : ι → α
, the elements of ι
on which f
gives ⊤
can be
dropped, without changing the result.
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This is a weaker version of sup_sInf_eq
This is a weaker version of inf_sSup_eq
This is a weaker version of sInf_sup_eq
This is a weaker version of sSup_inf_eq
Pullback a CompleteLattice
along an injection.
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