feat(ConditionallyCompleteLattice/Indexed): add binary versions of lemmas

Mathlib/Order/ConditionallyCompleteLattice/Indexed.lean

@@ -23,7 +23,7 @@ assert_not_exists Multiset
 
 open Function OrderDual Set
 
-variable {α β γ : Type*} {ι : Sort*}
+variable {α β γ : Type*} {ι : Sort*} {κ : ι → Sort*}
 
 section
 
@@ -136,9 +136,16 @@ theorem IsGLB.ciInf_set_eq {s : Set β} {f : β → α} (H : IsGLB (f '' s) a) (
   IsGLB.csInf_eq (image_eq_range f s ▸ H) (image_eq_range f s ▸ Hne.image f)
 
 /-- The indexed supremum of a function is bounded above by a uniform bound -/
+@[to_dual le_ciInf /-- The indexed minimum of a function is bounded below by a uniform
+lower bound -/]
 theorem ciSup_le [Nonempty ι] {f : ι → α} {c : α} (H : ∀ x, f x ≤ c) : iSup f ≤ c :=
   csSup_le (range_nonempty f) (by rwa [forall_mem_range])
 
+@[to_dual le_ciInf₂]
+theorem ciSup₂_le [Nonempty ι] [∀ i, Nonempty (κ i)] {f : ∀ i, κ i → α}
+    (h : ∀ i j, f i j ≤ a) : ⨆ (i) (j), f i j ≤ a :=
+  ciSup_le fun i ↦ ciSup_le <| h i
+
 /-- The indexed supremum of a function is bounded below by the value taken at one point -/
 theorem le_ciSup {f : ι → α} (H : BddAbove (range f)) (c : ι) : f c ≤ iSup f :=
   le_csSup H (mem_range_self _)
@@ -431,6 +438,12 @@ When `iInf f < a`, there is an element `i` such that `f i < a`.
 theorem exists_lt_of_ciInf_lt [Nonempty ι] {f : ι → α} (h : iInf f < a) : ∃ i, f i < a :=
   exists_lt_of_lt_ciSup (α := αᵒᵈ) h
 
+@[to_dual exists_lt_of_ciInf₂_lt]
+theorem exists_lt_of_lt_ciSup₂ [Nonempty ι] [∀ i, Nonempty (κ i)]
+    {f : ∀ i, κ i → α} (h : a < ⨆ (i) (j), f i j) : ∃ i j, a < f i j := by
+  contrapose! h
+  exact ciSup₂_le h
+
 theorem lt_ciSup_iff [Nonempty ι] {f : ι → α} (hb : BddAbove (range f)) :
     a < iSup f ↔ ∃ i, a < f i := by
   simpa only [mem_range, exists_exists_eq_and] using lt_csSup_iff hb (range_nonempty _)
@@ -531,6 +544,9 @@ theorem ciSup_le_iff' {f : ι → α} (h : BddAbove (range f)) {a : α} :
 theorem ciSup_le' {f : ι → α} {a : α} (h : ∀ i, f i ≤ a) : ⨆ i, f i ≤ a :=
   csSup_le' <| forall_mem_range.2 h
 
+theorem ciSup₂_le' {f : ∀ i, κ i → α} (h : ∀ i j, f i j ≤ a) : ⨆ (i) (j), f i j ≤ a :=
+  ciSup_le' fun i ↦ ciSup_le' <| h i
+
 @[simp]
 theorem ciSup_bot : ⨆ _ : ι, (⊥ : α) = ⊥ := le_bot_iff.mp (ciSup_le' fun _ ↦ bot_le)
 
@@ -543,6 +559,11 @@ theorem exists_lt_of_lt_ciSup' {f : ι → α} {a : α} (h : a < ⨆ i, f i) : 
   contrapose! h
   exact ciSup_le' h
 
+theorem exists_lt_of_lt_ciSup₂' {f : ∀ i, κ i → α} (h : a < ⨆ (i) (j), f i j) :
+    ∃ i j, a < f i j := by
+  contrapose! h
+  exact ciSup₂_le' h
+
 theorem ciSup_mono_of_forall_exists' {ι'} {f : ι → α} {g : ι' → α} (hg : BddAbove <| range g)
     (h : ∀ i, ∃ i', f i ≤ g i') : ⨆ i, f i ≤ ⨆ i', g i' :=
   ciSup_le' fun i ↦ h i |>.elim <| le_ciSup_of_le hg