Suppose you want to recursively remove certain things from a binding. If you write a function which will identify the elements to be removed, you can use this function to do the recursive removal for you: 

   1   /**nocache**/
   2   remove_by_predicate(b:binding, test:function)
   3   {
   4     /**nocache**/
   5     inner(n:text, v:any)
   6     {
   7       return (if test(n,v)
   8               then []
   9               else (if _is_binding(v) 
  10                     then [$n=_map(inner, v)]
  11                     else [$n=v]));
  12     };
  13     return _map(inner, b);
  14   };

You could use this as another way to RemoveByName: 

   1   /**nocache**/
   2   remove_by_name(b:binding, remove:text) {
   3     /**nocache**/
   4     test(n:text, v:any) {
   5       return (n == remove);
   6     };
   7     return remove_by_predicate(b, test);
   8   };

You could also use it to remove binding elements that represent deleted files in the result of a _run_tool call: 

   1   /**nocache**/
   2   remove_deleted(b: binding): binding
   3   {
   4     /**nocache**/
   5     test(n:text, v:any) {
   6       return (v == FALSE);
   7     };
   8     return remove_by_predicate(b, test);
   9   };