src/Pure/General/seq.ML

   | some => make (fn () => some));
 
 fun op APPEND (f, g) x =
   append (f x) (make (fn () => pull (g x)));
 
-fun EVERY fs = foldr THEN succeed fs;
-fun FIRST fs = foldr ORELSE fail fs;
+fun EVERY fs = fold_rev (curry op THEN) fs succeed;
+fun FIRST fs = fold_rev (curry op ORELSE) fs fail;
 
 fun TRY f = ORELSE (f, succeed);
 
 fun REPEAT f =
   let