@Diag and @Place

[Ludovic Court?s]

Hi,

I have a diagram where I would like to put a box at coordinates that are
relative to another box.  Here is what I'm doing:

  @Diag
  {
  @Tbl
  {
    [...]
  @Rowa
    B { X:: @Box { box } }
  } # @Tbl

  @Place x { { xcoord X } + 1f } y { ycoord address@hidden }  { @Box { other 
box } }

  //
  [...]
  } address@hidden

The Postscript file generated by Lout in this case is invalid even if the
@Place occurs after the "//" (the same code works fine without the @Place).
What's wrong with this code? Are "xcoord" and "ycoord" forbidden in this
context?

Thanks,
Ludovic.