IMP_Code_2

Como me quedaron las cosas:

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eval (Bin b e1 e2) = eval e1 >>= \res -> eval e2 >>= evalBin b res
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evalBin Lt  (VInt n1)  (VInt n2)   = return $ VBool (n1<n2)
evalBin Gt  (VInt n1)  (VInt n2)   = return $ VBool (n1>n2)
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exec (Block sts)     = executeAll (map exec sts)
exec (If ex st1 st2) = (eval ex >>= checkVBool) >>= (\cond -> if cond then exec st1 else exec st2)
exec (While ex st)   = (eval ex >>= checkVBool) >>= (\cond -> if cond then (exec st) >>= (\v -> exec $ While ex st) else return ())
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executeAll :: [Interpreter ()] -> Interpreter ()
executeAll []     = return ()
executeAll (i:is) = i >>= (\v -> executeAll is)