src/Pure/General/table.ML

   val forall: (key * 'a -> bool) -> 'a table -> bool
   val defined: 'a table -> key -> bool
   val lookup: 'a table * key -> 'a option
   val update: (key * 'a) * 'a table -> 'a table
   val update_new: (key * 'a) * 'a table -> 'a table                    (*exception DUP*)
-  val default: key -> 'a -> 'a table -> 'a table
+  val default: key * 'a -> 'a table -> 'a table
   val map_entry: key -> ('a -> 'a) -> 'a table -> 'a table
   val make: (key * 'a) list -> 'a table                                (*exception DUPS*)
   val extend: 'a table * (key * 'a) list -> 'a table                   (*exception DUPS*)
   val join: (key -> 'a * 'a -> 'a option) ->
     'a table * 'a table -> 'a table                                    (*exception DUPS*)

     handle SAME => tab
   end;
 
 fun update ((key, x), tab) = modify key (fn _ => x) tab;
 fun update_new ((key, x), tab) = modify key (fn NONE => x | SOME _ => raise DUP key) tab;
-fun default key x tab = if defined tab key then tab else update ((key, x), tab)
+fun default (p as (key, x)) tab = if defined tab key then tab else update (p, tab)
 fun map_entry key f = modify key (fn NONE => raise SAME | SOME x => f x);
 
 
 (* extend and make *)