use bset instead of dom

Author: leouk

vdmlib/src/main/resources/Bag.vdmsl

@@ -105,7 +105,7 @@ functions
        munion 
        (bset[@T](a) <-: b) 
        munion 
-       { x |-> a(x) + b(x) | x in set dom a inter dom b }
+       { x |-> a(x) + b(x) | x in set bset[@T](a) inter bset[@T](b) }
     pre 
         type_convergent[@T](a) and type_convergent[@T](b)
     post 

vdmlib/src/main/resources/StrBag.vdmsl

@@ -86,7 +86,7 @@ functions
        munion 
        (bset(a) <-: b) 
        munion 
-       { x |-> a(x) + b(x) | x in set dom a inter dom b }
+       { x |-> a(x) + b(x) | x in set bset(a) inter bset(b) }
     post 
         bset(RESULT) = bset(a) union bset(b)
         and