Expose decidability from Map modules

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

Lattice/FiniteMap.agda

@@ -27,6 +27,7 @@ open import Lattice.Map A B _≈₂_ _⊔₂_ _⊓₂_ ≡-dec-A lB as Map
         ; ⊓-idemp to ⊓ᵐ-idemp
         ; absorb-⊔-⊓ to absorb-⊔ᵐ-⊓ᵐ
         ; absorb-⊓-⊔ to absorb-⊓ᵐ-⊔ᵐ
+        ; ≈-dec to ≈ᵐ-dec
         )
 open import Data.Product using (_×_; _,_; Σ; proj₁ ; proj₂)
 open import Equivalence
@@ -38,6 +39,9 @@ module _ (ks : List A) where
     _≈_ : FiniteMap → FiniteMap → Set (a ⊔ℓ b)
     _≈_ (m₁ , _) (m₂ , _) = m₁ ≈ᵐ m₂
 
+    ≈-dec : IsDecidable _≈₂_ → IsDecidable _≈_
+    ≈-dec ≈₂-dec fm₁ fm₂ = ≈ᵐ-dec ≈₂-dec (proj₁ fm₁) (proj₁ fm₂)
+
     _⊔_ : FiniteMap → FiniteMap → FiniteMap
     _⊔_ (m₁ , km₁≡ks) (m₂ , km₂≡ks) = (m₁ ⊔ᵐ m₂ , trans (sym (⊔-equal-keys {m₁} {m₂} (trans (km₁≡ks) (sym km₂≡ks)))) km₁≡ks)