diff --git a/Analysis/Sign.agda b/Analysis/Sign.agda
index 1fc555f..ca45e0f 100644
--- a/Analysis/Sign.agda
+++ b/Analysis/Sign.agda
@@ -13,6 +13,7 @@ open import Function using (_∘_)
 open import Language
 open import Lattice
 open import Utils using (Pairwise)
+open import Showable using (Showable; show)
 import Lattice.FiniteValueMap
 
 data Sign : Set where
@@ -20,6 +21,16 @@ data Sign : Set where
     - : Sign
     0ˢ : Sign
 
+instance
+    showable : Showable Sign
+    showable = record
+        { show = (λ
+            { + → "+"
+            ; - → "-"
+            ; 0ˢ → "0"
+            })
+        }
+
 -- g for siGn; s is used for strings and i is not very descriptive.
 _≟ᵍ_ : IsDecidable (_≡_ {_} {Sign})
 _≟ᵍ_ + + = yes refl
@@ -301,20 +312,7 @@ module WithProg (prog : Program) where
     open import Data.String using (_++_)
     open import Data.List using () renaming (length to lengthˡ)
 
-    showAboveBelow : AB.AboveBelow → String
-    showAboveBelow AB.⊤ = "⊤"
-    showAboveBelow AB.⊥ = "⊥"
-    showAboveBelow (AB.[_] +) = "+"
-    showAboveBelow (AB.[_] -) = "-"
-    showAboveBelow (AB.[_] 0ˢ) = "0"
-
-    showVarSigns : VariableSigns → String
-    showVarSigns ((kvs , _) , _) = "{" ++ foldr (λ (x , y) rest → x ++ " ↦ " ++ showAboveBelow y ++ ", " ++ rest) "" kvs ++ "}"
-
-    showStateVars : StateVariables → String
-    showStateVars ((kvs , _) , _) = "{" ++ foldr (λ (x , y) rest → (showFin x) ++ " ↦ " ++ showVarSigns y ++ ", " ++ rest) "" kvs ++ "}"
-
-    output = showStateVars signs
+    output = show signs
 
 
 -- Debugging code: construct and run a program.
diff --git a/Lattice/AboveBelow.agda b/Lattice/AboveBelow.agda
index 1ee94ae..970968a 100644
--- a/Lattice/AboveBelow.agda
+++ b/Lattice/AboveBelow.agda
@@ -11,6 +11,7 @@ open import Data.Empty using (⊥-elim)
 open import Data.Product using (_,_)
 open import Data.Nat using (_≤_; ℕ; z≤n; s≤s; suc)
 open import Function using (_∘_)
+open import Showable using (Showable; show)
 open import Relation.Binary.PropositionalEquality as Eq
     using (_≡_; sym; subst; refl)
 
@@ -24,6 +25,16 @@ data AboveBelow : Set a where
     ⊤ : AboveBelow
     [_] : A → AboveBelow
 
+instance
+    showable : {{ showableA : Showable A }} → Showable AboveBelow
+    showable = record
+        { show = (λ
+            { ⊥ → "⊥"
+            ; ⊤ → "⊤"
+            ; [ a ] → show a
+            })
+        }
+
 data _≈_ : AboveBelow → AboveBelow → Set a where
     ≈-⊥-⊥ : ⊥ ≈ ⊥
     ≈-⊤-⊤ : ⊤ ≈ ⊤
diff --git a/Lattice/FiniteMap.agda b/Lattice/FiniteMap.agda
index 883914f..59d2f36 100644
--- a/Lattice/FiniteMap.agda
+++ b/Lattice/FiniteMap.agda
@@ -45,11 +45,17 @@ open import Function using (_∘_)
 open import Relation.Nullary using (¬_; Dec; yes; no)
 open import Utils using (Pairwise; _∷_; [])
 open import Data.Empty using (⊥-elim)
+open import Showable using (Showable; show)
 
 module WithKeys (ks : List A) where
     FiniteMap : Set (a ⊔ℓ b)
     FiniteMap = Σ Map (λ m → Map.keys m ≡ ks)
 
+    instance
+        showable : {{ showableA : Showable A }} {{ showableB : Showable B }} →
+                   Showable FiniteMap
+        showable = record { show = λ (m₁ , _) → show m₁ }
+
     _≈_ : FiniteMap → FiniteMap → Set (a ⊔ℓ b)
     _≈_ (m₁ , _) (m₂ , _) = m₁ ≈ᵐ m₂
 
diff --git a/Lattice/Map.agda b/Lattice/Map.agda
index afc86cd..cc7f0ea 100644
--- a/Lattice/Map.agda
+++ b/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)
 
diff --git a/Showable.agda b/Showable.agda
new file mode 100644
index 0000000..62d4548
--- /dev/null
+++ b/Showable.agda
@@ -0,0 +1,38 @@
+module Showable where
+
+open import Data.String using (String; _++_)
+open import Data.Nat using (ℕ)
+open import Data.Nat.Show using () renaming (show to showNat)
+open import Data.Fin using (Fin)
+open import Data.Fin.Show using () renaming (show to showFin)
+open import Data.Product using (_×_; _,_)
+open import Data.Unit using (⊤; tt)
+
+record Showable {a} (A : Set a) : Set a where
+    field
+        show : A → String
+
+open Showable {{ ... }} public
+
+instance
+    showableString : Showable String
+    showableString = record { show = λ s → "\"" ++ s ++ "\"" }
+
+    showableNat : Showable ℕ
+    showableNat = record { show = showNat }
+
+    showableFin : ∀ {n : ℕ} → Showable (Fin n)
+    showableFin = record { show = showFin }
+
+    showableProd : ∀ {a b} {A : Set a} {B : Set b}
+                     {{ showableA : Showable A }} {{ showableB : Showable B }} →
+                   Showable (A × B)
+    showableProd {{ showableA }} {{ showableB }} = record
+        { show = λ (a , b) →
+            "(" ++ show a ++
+            ", " ++ show b ++
+            ")"
+        }
+
+    showableUnit : Showable ⊤
+    showableUnit = record { show = λ tt → "()" }