>From [http://www.xdmf.org/index.php/XDMF_Model_and_Format] regarding the Xdmf 
>Function DataItem: "The function description can be arbitrarily complex and 
>contain SIN, COS, TAN, ACOS..."

However, I noticed that operations as simple as multiplication by a constant 
are tricky: In Paraview 3.8.1,

Function=" 2.3 * $0 "

will apparently multiply the DataItem referenced by $0 by the _integer_ part of 
the constant factor (2.0 in this case)! This is especially nasty if you plan to 
multiply by something between 0 and 1, which will consequently reduce all 
values of $0 to zero. The same seems to apply to *division* by a non-integer 
constant.
A multiplication by, say, 1.5 can be achieved using something like

Function=" $0 * (3/2) " or Function=" ($0 / 2)*3" .

Note also that things like

Function=" (1.2+0.1) * $0 "

will segfault (at least on my machine).
The XMDF file quoted below may serve to illustrate this issue.

If this problem can be confirmed, I propose to at least add a corresponding 
comment to the XDMF wiki.

Cheers, Jens.

------------------ BEGIN test_function2.xmf ----------------------------
<?xml version="1.0" ?>
<!DOCTYPE Xdmf SYSTEM "Xdmf.dtd" []>
<Xdmf Version="2.0">
  <Domain>
    <Grid Name="ftest2_grid" GridType="Uniform">
      <Topology TopologyType="2dCoRectMesh" Dimensions="2 2"/>
      <Geometry GeometryType="Origin_DxDyDz">
        <DataItem Dimensions="2" NumberType="Float" Format="XML">
          0.0  0.0
        </DataItem>
        <DataItem Dimensions="2" NumberType="Float" Format="XML">
          1.0  1.0
        </DataItem>
      </Geometry>
      <Attribute Name="func(Data)" AttributeType="Scalar" Center="Node">
        <DataItem Dimensions="2 2" ItemType="Function"
                  Function=" 2.3 * $0 ">
          <DataItem Name="arr_4x4" Dimensions="2 2" Format="XML">
            1.0 2.0 3.0 4.0
          </DataItem>
        </DataItem> 
      </Attribute>
    </Grid>
  </Domain>
</Xdmf>
-------------------- END test_function2.xmf ----------------------------
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