Sovle homework 4

HW4Part1.hs

@@ -0,0 +1,46 @@
+module HW4Part1 where
+
+data Reg = A | B | R
+
+data Expr
+    = Lit Int
+    | Reg Reg
+    | Plus Expr Expr
+    | Leq Expr Expr
+    | Not Expr
+
+type Prog = [Stmt]
+
+data Stmt
+    = Store Reg Expr
+    | If Expr Prog Prog
+    | Loop Prog
+    | Break
+
+program :: Prog
+program =
+    [ Store A $ Lit 7
+    , Store B $ Lit 9
+    , Store R $ Lit 0
+    , Loop $
+        [ If (Reg A `Leq` Lit 0)
+            [ Break ]
+            [ Store R $ Reg R `Plus` Reg B
+            , Store A $ Reg A `Plus` Lit (-1)
+            ]
+        ]
+    ]
+
+while :: Expr -> Prog -> Stmt
+while cond body = Loop $ If cond [] [ Break ] : body
+
+sumFromTo :: Int -> Int -> Prog
+sumFromTo f t =
+    [ Store A $ Lit f
+    , Store B $ Lit t
+    , Store R $ Lit 0
+    , while (Leq (Reg A) (Reg B))
+        [ Store R $ Reg R `Plus` Reg A
+        , Store A $ Reg A `Plus` (Lit 1)
+        ]
+    ]