Assigning to Element of Array of Records Doesn't Seem to Work

I'm just trying to assign to a field of a record in a one-dimensional
array of records, but I get this incomprehensible message:
=====================================================================
(1) -> )clear all
   All user variables and function definitions have been cleared.
(1) -> )read foo.input
-- File of Axiom definitions solving problem 124.
-- Created 2007/08/08 by Bill Wood.

init_rec() ==
  r : Record(k: INT, rad: INT) := [0,0]
  r

                                           Type: Void
(2) -> xs := [init_rec() for i in 1..3]
   Compiling function initrec with type () -> Record(k: Integer,rad:
      Integer)

   (2)  [[k= 0,rad= 0],[k= 0,rad= 0],[k= 0,rad= 0]]
                      Type: List Record(k: Integer,rad: Integer)
(3) -> ys := oneDimensionalArray(xs)
(3) ->
   (3)  [[k= 0,rad= 0],[k= 0,rad= 0],[k= 0,rad= 0]]
           Type: OneDimensionalArray Record(k: Integer,rad: Integer)
(4) -> ys
(4) ->
   (4)  [[k= 0,rad= 0],[k= 0,rad= 0],[k= 0,rad= 0]]
           Type: OneDimensionalArray Record(k: Integer,rad: Integer)
(5) -> ys(2).k := 10
 5) ->
   The form on the left hand side of an assignment must be a single
      variable, a Tuple of variables or a reference to an entry in an
      object supporting the setelt operation.
(5) ->
=======================================================================
What do I have to do to set the fields of the records to desired
values???

 -- Bill Wood