Use instances to simplify printing code

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

Lattice/Map.agda

@@ -13,13 +13,15 @@ open import Data.List.Membership.Propositional as MemProp using () renaming (_
 
 open import Relation.Nullary using (¬_; Dec; yes; no)
 open import Data.Nat using (ℕ)
-open import Data.List using (List; map; []; _∷_; _++_)
+open import Data.List using (List; map; []; _∷_; _++_) renaming (foldr to foldrˡ)
 open import Data.List.Relation.Unary.All using (All; []; _∷_)
 open import Data.List.Relation.Unary.Any using (Any; here; there) -- TODO: re-export these with nicer names from map
 open import Data.Product using (_×_; _,_; Σ; proj₁ ; proj₂)
 open import Data.Empty using (⊥; ⊥-elim)
 open import Equivalence
 open import Utils using (Unique; push; Unique-append; All¬-¬Any; All-x∈xs)
+open import Data.String using () renaming (_++_ to _++ˢ_)
+open import Showable using (Showable; show)
 
 open IsLattice lB using () renaming
     ( ≈-refl to ≈₂-refl; ≈-sym to ≈₂-sym; ≈-trans to ≈₂-trans
@@ -478,6 +480,14 @@ private module ImplInsert (f : B → B → B) where
 Map : Set (a ⊔ℓ b)
 Map = Σ (List (A × B)) (λ l → Unique (ImplKeys.keys l))
 
+instance
+    showable : {{ showableA : Showable A }} {{ showableB : Showable B }} →
+               Showable Map
+    showable = record
+        { show = λ (kvs , _) →
+            "{" ++ˢ foldrˡ (λ (x , y) rest → show x ++ˢ " ↦ " ++ˢ show y ++ˢ ", " ++ˢ rest) "" kvs ++ˢ "}"
+        }
+
 empty : Map
 empty = ([] , Utils.empty)