Nested properties in xacro

edit

I know you can nest xacro macros, but is it also possible to nest properties in xacro?

I'm trying something like this

test.xacro contains

<?xml version="1.0"?>
<robot
    xmlns:xacro="http://www.ros.org/wiki/xacro"
    name="test">

  <property name="foo" value="1.0"/>
  <property name="bar" value="${foo + 1.0}"/>

  <link name="test_link">
    <inertial>
      <origin xyz="${foo} ${bar} 0"/>
    </inertial>
  </link>
</robot>

but the output of rosrun xacro xacro.py test.xacro gives me:

<?xml version="1.0" ?>
...
<robot name="test" xmlns:xacro="http://www.ros.org/wiki/xacro">
<link name="test_link">
   <inertial>
      <origin xyz="1.0 ${foo + 1.0} 0"/>
   </inertial>
</link>
</robot>

note the not expanded contents of the bar property