fixed example program power

examples/programs/power.mlw

@@ -23,7 +23,7 @@ module M
     let p = ref x in
     let e = ref n in
     while !e > 0 do
-      invariant { r * power x e = power x n }
+      invariant { 0 <= e and r * power p e = power x n }
       variant   { e }
       if mod !e 2 = 1 then r := !r * !p;
       p := !p * !p;

theories/int.why

@@ -102,12 +102,15 @@ theory Power
 
   axiom Power_s : forall x n : int. 0 < n -> power x n = x * power x (n-1)
 
+  lemma Power_1 : forall x : int. power x 1 = x
+
   lemma Power_sum : forall x n m : int. 0 <= n -> 0 <= m ->
     power x (n + m) = power x n * power x m
 
   lemma Power_mult : forall x n m : int. 0 <= n -> 0 <= m ->
     power x (n * m) = power (power x n) m
 
+
 end
 
 theory NumOfParam