Make the sample programs actually run.

programs/data_decls.lily

@@ -1,2 +0,0 @@
-data Bool = { True, False }
-data IntList = { Nil, Cons(Int, IntList) }

programs/length.lily

@@ -1,6 +1,8 @@
+data IntList = { Nil, Cons(Int, IntList) }
 defn length l = {
     case l of {
         Nil -> { 0 }
         Cons(x, xs) -> { 1 + length xs }
     }
 }
+defn main = { length (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil)))) }

programs/not.lily

@@ -1,6 +1,14 @@
+data Bool = { True, False }
 defn not b = {
     case b of {
         False -> { True }
         True -> { False }
     }
 }
+defn booli b = {
+    case b of {
+        False -> { 0 }
+        True -> { 1 }
+    }
+}
+defn main = { booli (not False) }

programs/sum.lily

@@ -0,0 +1,8 @@
+data IntList = { Nil, Cons(Int, IntList) }
+defn sum l = {
+    case l of {
+        Nil -> { 0 }
+        Cons(x, xs) -> { x + sum xs }
+    }
+}
+defn main = { sum (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil)))) }