fixed polymorphic val;

--- a/src/Pure/net.ML	Wed Jul 23 11:07:36 1997 +0200
+++ b/src/Pure/net.ML	Wed Jul 23 11:11:14 1997 +0200
@@ -221,13 +221,12 @@
 (** dest **)
 
 fun cons_fst x (xs, y) = (x :: xs, y);
-val cons_fsts = map o cons_fst;
 
 fun dest (Leaf xs) = map (pair []) xs
   | dest (Net {comb, var, alist}) =
-      cons_fsts CombK (dest comb) @
-      cons_fsts VarK (dest var) @
-      flat (map (fn (a, net) => cons_fsts (AtomK a) (dest net)) alist);
+      map (cons_fst CombK) (dest comb) @
+      map (cons_fst VarK) (dest var) @
+      flat (map (fn (a, net) => map (cons_fst (AtomK a)) (dest net)) alist);
 
 
 (** merge **)