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Theorems · Theorem · order theory

ciSup_eq_of_forall_le_of_forall_lt_exists_gt

∀ {α : Type u_1} {ι : Sort u_4} [inst : ConditionallyCompleteLattice α] {b : α} [Nonempty ι] {f : ι → α},
  (∀ (i : ι), f i ≤ b) → (∀ w < b, ∃ i, w < f i) → ⨆ i, f i = b

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.

Defined in
Mathlib.Order.ConditionallyCompleteLattice.Indexed
Cited by
8 results in Mathlib
Foundations
Depth 17 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes
ConditionallyCompleteLatticeNonempty

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