bork

[clean-tests.git] / expr / exist / while.icl

diff --git a/expr/exist/while.icl b/expr/exist/while.icl
new file mode 100644 (file)
index 0000000..4e23327
--- /dev/null
+++ b/expr/exist/while.icl
@@ -0,0 +1,38 @@
+implementation module while
+
+import StdEnv
+
+:: Gamma :== String -> Int
+instance gamma Gamma
+where
+       put g i v = \i`->if (i == i`) v (g i)
+       get g v = g v
+
+emptyGamma :: Gamma
+emptyGamma = abort "Undefined variable"
+
+instance eval WhileExpr
+where
+       eval (i =. v)         = \g->put g i (evali v g)
+       eval (If b _ t _ e)   = \g->if (evalb b g) (eval t g) (eval e g)
+       eval (a :. b)         = eval b o eval a
+       eval x=:(While b _ e) = \g->if (evalb b g) (eval (e :. x) g) g
+       eval Skip             = id
+       eval (WExpr e)        = eval e
+
+instance evali WhileInt
+where
+       evali (Int i)  = const i
+       evali (Var s)  = flip get s
+       evali (a +. b) = \g->evali a g + evali b g
+       evali (WInt e) = evali e
+
+instance evalb WhileBool
+where
+       evalb (Bool b)  = const b
+       evalb (a ==. b) = \g->evali a g == evali b g
+       evalb (a &. b)  = \g->evalb a g && evalb b g
+       evalb (Not a)   = not o evalb a
+       evalb (WBool e) = evalb e
+
+Start = (eval ("a" =. Int 42 :. While (Bool False) Do ("b" =. Int 4)) emptyGamma) "a"