Add a 'set' lattice backed by maps

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

Lattice/MapSet.agda

@@ -0,0 +1,19 @@
+open import Lattice
+open import Relation.Binary.PropositionalEquality as Eq using (_≡_; refl; sym; trans; cong; subst)
+open import Relation.Binary.Definitions using (Decidable)
+open import Agda.Primitive using (Level) renaming (_⊔_ to _⊔ℓ_)
+
+module Lattice.MapSet {a : Level} (A : Set a) (≡-dec-A : Decidable (_≡_ {a} {A})) where
+
+open import Lattice.Unit using (⊤) renaming (_≈_ to _≈₂_; _⊔_ to _⊔₂_; _⊓_ to _⊓₂_; isLattice to ⊤-isLattice)
+import Lattice.Map
+
+private module UnitMap = Lattice.Map A ⊤ _≈₂_ _⊔₂_ _⊓₂_ ≡-dec-A ⊤-isLattice
+open UnitMap using (Map)
+open UnitMap using
+    ( _⊆_; _≈_; ≈-equiv; _⊔_; _⊓_
+    ; isUnionSemilattice; isIntersectSemilattice; isLattice
+    ) public
+
+MapSet : Set a
+MapSet = Map