diff --git a/ExtTreeMapLemmas/ExtDTreeMap.lean b/ExtTreeMapLemmas/ExtDTreeMap.lean
index 0017da9..c77620e 100644
--- a/ExtTreeMapLemmas/ExtDTreeMap.lean
+++ b/ExtTreeMapLemmas/ExtDTreeMap.lean
@@ -9,3 +9,5 @@ theorem ExtDTreeMap.get?_filter {cmp : α → α → Ordering} [TransCmp cmp]
     (m : ExtDTreeMap α (fun _ => β) cmp) (f : α → β → Bool) (k : α) :
     Const.get? (m.filter f) k = (Const.get? m k).pfilter (fun v h' => f (m.getKey k (Const.contains_eq_isSome_get?.trans (Option.isSome_of_eq_some h'))) v) :=
   m.inductionOn fun _ => DTreeMap.get?_filter _ _ _
+
+end Std
diff --git a/ExtTreeMapLemmas/ExtTreeMap.lean b/ExtTreeMapLemmas/ExtTreeMap.lean
index 931828f..d62251a 100644
--- a/ExtTreeMapLemmas/ExtTreeMap.lean
+++ b/ExtTreeMapLemmas/ExtTreeMap.lean
@@ -2,27 +2,40 @@ import ExtTreeMapLemmas.ExtDTreeMap
 import Std.Data.ExtTreeMap.Lemmas
 import Mathlib.Tactic
 
-theorem Std.ExtTreeMap.getElem?_pfilter {cmp : α → α → Ordering} [TransCmp cmp]
-    (m : ExtTreeMap α β cmp) (f : α → β → Bool) (k : α) :
-    (m.filter f)[k]? = m[k]?.pfilter (fun v h' => f (m.getKey k (contains_eq_isSome_getElem?.trans (Option.isSome_of_eq_some h'))) v) :=
-  ExtDTreeMap.get?_filter m.inner f k
+namespace Std.ExtTreeMap
 
-open Std
-namespace ExtTreeMap
+variable {α β : Type}
 
 attribute [local instance low] beqOfOrd
-variable {α β : Type} {cmp : α → α → Ordering} [TransCmp cmp] [LawfulEqCmp cmp]
+attribute [grind ext] ExtTreeMap.ext_getElem?
+attribute [grind] ExtTreeMap.distinct_keys_toList ExtTreeMap.getElem?_ofList_of_mem
+
+@[grind =]
+theorem getElem?_pfilter
+  {cmp : α → α → Ordering} [TransCmp cmp]
+  {m : ExtTreeMap α β cmp} {f : α → β → Bool} {k : α} :
+  (m.filter f)[k]? =
+  m[k]?.pfilter (fun v h' => f (m.getKey k (contains_eq_isSome_getElem?.trans (Option.isSome_of_eq_some h'))) v) :=
+  ExtDTreeMap.get?_filter m.inner f k
+
+variable {α β : Type} {cmp : α → α → Ordering}
 variable {k : α} {m m₁ m₂ : Std.ExtTreeMap α β cmp} {f : α → β → β → β}
 
+@[simp, grind =]
+lemma filter_empty {f : α → β → Bool} :
+  filter f (∅ : Std.ExtTreeMap α β cmp) = ∅ := rfl
+
+variable [TransCmp cmp] [LawfulEqCmp cmp]
+
 -- Pointwise characterization of `mergeWith` on optional access at a key.
 theorem get?_mergeWith_at
-    (m₁ m₂ : ExtTreeMap α β cmp) (f : α → β → β → β) (k : α) :
-    (m₁.mergeWith f m₂)[k]? =
-      match m₁[k]?, m₂[k]? with
-      | .some v₁, .some v₂ => .some (f k v₁ v₂)
-      | .some v₁, .none    => .some v₁
-      | .none,    .some v₂ => .some v₂
-      | .none,    .none    => .none := by
+  {m₁ m₂ : ExtTreeMap α β cmp} {f : α → β → β → β} {k : α} :
+  (m₁.mergeWith f m₂)[k]? =
+  match m₁[k]?, m₂[k]? with
+  | .some v₁, .some v₂ => .some (f k v₁ v₂)
+  | .some v₁, .none    => .some v₁
+  | .none,    .some v₂ => .some v₂
+  | .none,    .none    => .none := by
   let merge_values : Option β → Option β → Option β := fun
     | .some v₁, .some v₂ => .some (f k v₁ v₂)
     | .some v₁, .none    => .some v₁
@@ -41,114 +54,79 @@ theorem get?_mergeWith_at
           cases h₂ : DTreeMap.Const.get? t₂ k <;>
           simp [merge_values, DTreeMap.Const.get?_mergeWith, h₁, h₂]
 
-@[grind=]
-lemma mergeWith₀ (h₁ : k ∈ m₁) (h₂ : k ∈ m₂) :
+lemma mergeWith_of_mem_mem (h₁ : k ∈ m₁) (h₂ : k ∈ m₂) :
   (m₁.mergeWith f m₂)[k]? = .some (f k m₁[k] m₂[k]) := by
   have h₁' : m₁[k]? = .some m₁[k] :=
-    Std.ExtTreeMap.getElem?_eq_some_getElem (t := m₁) (a := k) h₁
+    getElem?_eq_some_getElem (t := m₁) (a := k) h₁
   have h₂' : m₂[k]? = .some m₂[k] :=
-    Std.ExtTreeMap.getElem?_eq_some_getElem (t := m₂) (a := k) h₂
+    getElem?_eq_some_getElem (t := m₂) (a := k) h₂
   simp only [get?_mergeWith_at, h₁', h₂']
 
-@[grind=]
-lemma mergeWith₁ (h₁ : k ∈ m₁) (h₂ : k ∉ m₂) :
+lemma mergeWith_of_mem_left (h₁ : k ∈ m₁) (h₂ : k ∉ m₂) :
   (m₁.mergeWith f m₂)[k]? = m₁[k]? :=  by
   have h₁' : m₁[k]? = .some m₁[k] :=
-    Std.ExtTreeMap.getElem?_eq_some_getElem (t := m₁) (a := k) h₁
+    getElem?_eq_some_getElem (t := m₁) (a := k) h₁
   have h₂' : m₂[k]? = .none :=
-    Std.ExtTreeMap.getElem?_eq_none (t := m₂) (a := k) h₂
+    getElem?_eq_none (t := m₂) (a := k) h₂
   simp only [get?_mergeWith_at, h₁', h₂']
 
-@[grind=]
-lemma mergeWith₂ (h₁ : k ∉ m₁) (h₂ : k ∈ m₂) :
+lemma mergeWith_of_mem_right (h₁ : k ∉ m₁) (h₂ : k ∈ m₂) :
   (m₁.mergeWith f m₂)[k]? = m₂[k]? := by
   have h₁' : m₁[k]? = .none :=
-    Std.ExtTreeMap.getElem?_eq_none (t := m₁) (a := k) h₁
+    getElem?_eq_none (t := m₁) (a := k) h₁
   have h₂' : m₂[k]? = .some m₂[k] :=
-    Std.ExtTreeMap.getElem?_eq_some_getElem (t := m₂) (a := k) h₂
+    getElem?_eq_some_getElem (t := m₂) (a := k) h₂
   simp only [get?_mergeWith_at, h₁', h₂']
 
-@[grind=]
-lemma mergeWith₃ (h₁ : k ∉ m₁) (h₂ : k ∉ m₂) :
+lemma mergeWith_of_not_mem (h₁ : k ∉ m₁) (h₂ : k ∉ m₂) :
   (m₁.mergeWith f m₂)[k]? = .none := by
   have h₁' : m₁[k]? = .none :=
-    Std.ExtTreeMap.getElem?_eq_none (t := m₁) (a := k) h₁
+    getElem?_eq_none (t := m₁) (a := k) h₁
   have h₂' : m₂[k]? = .none :=
-    Std.ExtTreeMap.getElem?_eq_none (t := m₂) (a := k) h₂
+    getElem?_eq_none (t := m₂) (a := k) h₂
   simp only [get?_mergeWith_at, h₁', h₂']
 
-@[simp, grind=]
-lemma mergeWith_empty {f : α → β → β → β} {cmp : α → α → Ordering} [Std.TransCmp cmp] [Std.LawfulEqCmp cmp]
-  {t : Std.ExtTreeMap α β cmp} :
-  Std.ExtTreeMap.mergeWith f t ∅ = t
-:= by ext; grind
+grind_pattern mergeWith_of_mem_mem => k ∈ m₁, k ∈ m₂, ExtTreeMap.mergeWith f m₁ m₂
+grind_pattern mergeWith_of_mem_left => k ∈ m₁, ExtTreeMap.mergeWith f m₁ m₂
+grind_pattern mergeWith_of_mem_right => k ∈ m₂, ExtTreeMap.mergeWith f m₁ m₂
+grind_pattern mergeWith_of_not_mem => (ExtTreeMap.mergeWith f m₁ m₂)[k]?
 
-lemma mergeWith_of_comm (h : ∀ {x}, Std.Commutative (f x)) :
-    m₁.mergeWith f m₂ = m₂.mergeWith f m₁ := by
-  ext k v
-  by_cases h' : k ∈ m₁ <;> by_cases h'' : k ∈ m₂
-  · rw [mergeWith₀ h' h'', mergeWith₀ h'' h', h.comm]
-  · rw [mergeWith₁ h' h'', mergeWith₂ h'' h']
-  · rw [mergeWith₂ h' h'', mergeWith₁ h'' h']
-  · rw [mergeWith₃ h' h'', mergeWith₃ h'' h']
-
-@[simp, grind=]
-lemma filter_empty {α : Type} {f : α → β → Bool} {cmp : α → α → Ordering} : Std.ExtTreeMap.filter f (∅ : Std.ExtTreeMap α β cmp) = ∅ := by
-  rfl
-
-variable [BEq α] [LawfulBEq α]
-
-@[simp, grind=]
-lemma toList_ofList {a : Std.ExtTreeMap α β cmp} : @Std.ExtTreeMap.ofList α β (@Std.ExtTreeMap.toList α β cmp _ a) cmp = a := by
-  ext k v
-  revert v
-  by_cases h : ∃ v, (k, v) ∈ a.toList
-  · rcases h with ⟨v, h⟩
-    rw [@Std.ExtTreeMap.getElem?_ofList_of_mem α β cmp _ a.toList k k (by grind) v Std.ExtTreeMap.distinct_keys_toList h]
-    rw [Std.ExtTreeMap.mem_toList_iff_getElem?_eq_some] at h
-    rw [h]
-    simp
-  · simp only [Std.ExtTreeMap.mem_toList_iff_getElem?_eq_some, not_exists] at h
-    intros v
-    simp only [h v, iff_false]
-    rw [Std.ExtTreeMap.getElem?_ofList_of_contains_eq_false]
-    · simp
-    · simp
-      intros h'
-      rw [←Std.ExtTreeMap.isSome_getKey?_iff_mem] at h'
-      aesop
-
-grind_pattern mergeWith₀ => k ∈ m₁, k ∈ m₂, ExtTreeMap.mergeWith f m₁ m₂
-grind_pattern mergeWith₁ => k ∈ m₁, k ∈ m₂, ExtTreeMap.mergeWith f m₁ m₂
-grind_pattern mergeWith₂ => k ∈ m₁, k ∈ m₂, ExtTreeMap.mergeWith f m₁ m₂
-grind_pattern mergeWith₃ => (ExtTreeMap.mergeWith f m₁ m₂)[k]?
+@[simp]
+lemma mergeWith_empty {f : α → β → β → β}
+                      {cmp : α → α → Ordering} [Std.TransCmp cmp] [Std.LawfulEqCmp cmp]
+                      {t : ExtTreeMap α β cmp} :
+  mergeWith f t ∅ = t := by grind
 
 @[grind =]
-lemma getElem?_filter {α β : Type} [BEq α] [LawfulBEq α]
-                      {cmp : α → α → Ordering} [Std.TransCmp cmp] [Std.LawfulEqCmp cmp]
-  {f : α → β → Bool} {k : α} {m : Std.ExtTreeMap α β cmp} :
+lemma mergeWith_of_comm (h : ∀ {x}, Std.Commutative (f x)) :
+  m₁.mergeWith f m₂ = m₂.mergeWith f m₁ := by
+  have {k} := @Commutative.comm (op := f k) _ (@h _)
+  grind
+
+@[simp, grind =]
+lemma toList_ofList [BEq α] [LawfulBEq α] : ofList (toList m) cmp = m := by
+  grind
+
+@[simp, grind =]
+lemma getElem?_filter {β : Type} {f : α → β → Bool} {k : α} {m : ExtTreeMap α β cmp} :
   (m.filter f)[k]? = m[k]?.filter (f k) := by
-  rw [Std.ExtTreeMap.getElem?_pfilter]
-  simp
-
-@[grind=]
-lemma filter_mem {f : α → β → Bool} {m : Std.ExtTreeMap α β cmp} (h : k ∈ m) : f k m[k] → (Std.ExtTreeMap.filter f m)[k]? = .some m[k] := by
-  intro h'
-  rw [getElem?_filter]
-  simp only [h, getElem?_pos, Option.filter_eq_some_iff, true_and]
-  exact h'
-
-@[grind=]
-lemma filter_not_mem {f : α → β → Bool} {m : Std.ExtTreeMap α β cmp} (h : k ∉ m) : (Std.ExtTreeMap.filter f m)[k]? = .none := by
-  rw [getElem?_filter]
-  simp [h]
-
-@[grind=]
-lemma filter_not_pred {f : α → β → Bool} {m : Std.ExtTreeMap α β cmp} (h : k ∈ m) : ¬ (f k m[k]) → (Std.ExtTreeMap.filter f m)[k]? = .none := by
-  intros h
-  rw [getElem?_filter]
+  simp [ExtTreeMap.getElem?_pfilter]
+
+variable {f : α → β → Bool}
+
+@[grind =]
+lemma filter_mem (h : k ∈ m) : f k m[k] → (filter f m)[k]? = .some m[k] := by
+  grind
+
+omit [LawfulEqCmp cmp] in
+@[grind =]
+lemma filter_not_mem (h : k ∉ m) : (filter f m)[k]? = .none := by
+  grind
+
+@[grind =]
+lemma filter_not_pred (h : k ∈ m) : ¬ (f k m[k]) → (filter f m)[k]? = .none := by
   grind
 
 attribute [grind ext] ExtTreeMap.ext_getElem?
 
-end ExtTreeMap
+end Std.ExtTreeMap
diff --git a/Main.lean b/Main.lean
deleted file mode 100644
index 830f903..0000000
--- a/Main.lean
+++ /dev/null
@@ -1,4 +0,0 @@
-import ExtTreeMapLemmas
-
-def main : IO Unit :=
-  IO.println s!"Hello!"
diff --git a/lakefile.lean b/lakefile.lean
new file mode 100644
index 0000000..ffaceda
--- /dev/null
+++ b/lakefile.lean
@@ -0,0 +1,10 @@
+import Lake
+
+open System Lake DSL
+
+package ExtTreeMapLemmas where version := v!"0.1.0"
+
+require "leanprover-community" / mathlib @ git "v4.22.0-rc2"
+
+@[default_target]
+lean_lib ExtTreeMapLemmas
diff --git a/lakefile.toml b/lakefile.toml
deleted file mode 100644
index 59c9250..0000000
--- a/lakefile.toml
+++ /dev/null
@@ -1,15 +0,0 @@
-name = "ExtTreeMapLemmas"
-version = "0.1.0"
-defaultTargets = ["exttreemaplemmas"]
-
-[[lean_lib]]
-name = "ExtTreeMapLemmas"
-
-[[lean_exe]]
-name = "exttreemaplemmas"
-root = "Main"
-
-[[require]]
-name = "mathlib"
-scope = "leanprover-community"
-rev = "v4.22.0-rc2"