gadt shit

diff --git a/a12/charlie/skeleton12_gadt.icl b/a12/charlie/skeleton12_gadt.icl
new file mode 100644 (file)
index 0000000..58da675
--- /dev/null
+++ b/a12/charlie/skeleton12_gadt.icl
@@ -0,0 +1,36 @@
+module skeleton12
+
+import StdEnv
+import StdMaybe
+
+:: BM a b = {t :: a -> b, f :: b -> a}                                          
+bm :: BM a a
+bm = {f=id, t=id}
+:: Expr a
+       = Lit (BM a Int) Int
+       | Add (BM a Int) (Expr a) (Expr a)
+       | Mul (BM a Int) (Expr a) (Expr a)
+       | Read
+       | Write (BM a a) (Expr a)
+       | XOR (BM a a) (Expr a) (Expr a)
+       | Not (BM a a) (Expr a)
+       | E.b: Eq (BM b a) (Expr b) (Expr b) & == b
+       | Throw
+       | Try (BM a a) (BM a a)
+
+class show a where
+       show :: (a t) [String] -> [String] | toString t
+
+instance show Expr where
+       show (Lit bm x) xs = [toString x:xs]
+       show (Add bm x y) xs = show x ["+":show y xs]
+       show (Mul bm x y) xs = show x ["*":show y xs]
+       show Read xs = ["read":xs]
+       show (Write bm x) xs = ["write":show x xs]
+       show (XOR bm x y) xs = show x ["XOR":show y xs]
+       show (Not bm x) xs = show x xs
+       show (Eq bm x y) xs = show x ["==":show y xs]
+       show Throw xs = ["throw":xs]
+       show (Try x y) xs = ["try":show x ["catch":show y xs]]
+
+Start = 1