Progress towards UFDs (#88)

Lists/Definition.agda

@@ -0,0 +1,18 @@
+{-# OPTIONS --safe --warning=error --without-K #-}
+
+open import LogicalFormulae
+open import Functions
+
+module Lists.Definition {a : _} where
+
+data List (A : Set a) : Set a where
+  [] : List A
+  _::_ : (x : A) (xs : List A) → List A
+infixr 10 _::_
+
+[_] : {A : Set a} → (a : A) → List A
+[ a ] = a :: []
+
+_++_ : {A : Set a} → List A → List A → List A
+[] ++ m = m
+(x :: l) ++ m = x :: (l ++ m)