Indexed sup / inf in conditionally complete lattices #
This file proves lemmas about iSup and iInf for functions valued in a conditionally complete,
rather than complete, lattice. We add a prefix c to distinguish them from the versions for
complete lattices, giving names ciSup_xxx or ciInf_xxx.
The indexed supremum of a function is bounded above by a uniform bound
If the set of all f i j is bounded above, then so is the set of the supremums of every row
The indexed suprema of two functions are comparable if the functions are pointwise comparable
The indexed infimum of two functions are comparable if the functions are pointwise comparable
The indexed minimum of a function is bounded below by a uniform lower bound
If the set of all f i j is bounded below, then so is the set of the infimums of every row
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<b.
See iSup_eq_of_forall_le_of_forall_lt_exists_gt for a version in 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 iInf_eq_of_forall_ge_of_forall_gt_exists_lt for a version in complete lattices.
Indexed version of exists_lt_of_lt_csSup.
When b < iSup f, there is an element i such that b < f i.
Indexed version of exists_lt_of_csInf_lt.
When iInf f < a, there is an element i such that f i < a.
Lemmas about a conditionally complete linear order with bottom element #
In this case we have Sup ∅ = ⊥, so we can drop some Nonempty/Set.Nonempty assumptions.
In conditionally complete orders with a bottom element, the nonempty condition can be omitted
from ciSup_le_iff.
In conditionally complete orders with a bottom element, the nonempty condition can be omitted
from lt_ciSup_iff.