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Function definitions#

You can define your own functions in the layout file. The following example defines a function called add which takes two arguments and calls it in the <Message> command:

layout.xml
<Layout xmlns="urn:speedata.de/2021/xts/en"
    xmlns:sd="urn:speedata.de/2021/xtsfunctions/en"
    xmlns:fn="mynamespace">

    <Record element="data">
        <Message select=" fn:add(4,3) "/>
    </Record>

    <Function name="fn:add">
        <Param name="first" />
        <Param name="second" />
        <Value select="$first + $second " />
    </Function>
</Layout>

The output in the protocol file is

info    Message (line 7): 7.000000

which is what we should expect.

There are a few things to mention:

  • The namespace of the function must be defined in the root element.
  • You can output objects in a function definition.
  • Variables have a local scope.

  • Every command that has a return value contributes to the output of the function:

    The following function definition returns a sequence of two values:

    <Function name="fn:mult-and-add">
    <Param name="first" />
    <Param name="second" />
    <Value select="$first * $second "></Value>
    <Value select="$first + $second "></Value>
</Function>

A more complex example#

<Layout xmlns="urn:speedata.de/2021/xts/en"
    xmlns:sd="urn:speedata.de/2021/xtsfunctions/en"
    xmlns:fn="mynamespace">

    <Stylesheet scope="layout"> Td { border: 1pt solid black; } </Stylesheet>
    <Record element="data">
        <PlaceObject>
            <Table>
                <!-- this is one argument (a sequence with two items) -->
                <Value select="fn:cols(('2cm','3cm'))" />
                <Tr>
                    <Td>
                        <Paragraph><Value>two cm</Value></Paragraph>
                    </Td>
                    <Td>
                        <Paragraph><Value>three cm</Value></Paragraph>
                    </Td>
                </Tr>
            </Table>
        </PlaceObject>
    </Record>

    <Function name="fn:cols">
        <Param name="colspec" />
        <Columns>
            <ForAll select="$colspec">
                <Column width="{.}" />
            </ForAll>
        </Columns>
    </Function>
</Layout>

<data>
</data>

a simple table

Here the function fn:cols is defined with one parameter. This function is called with one argument: a sequence of two strings. This sequence is stored in the variable colspec. The <ForAll> loop iterates over this sequence and builds the following XML elements:

<Columns>
    <Column width="2cm" />
    <Column width="3cm" />
</Columns>

The curly braces jump into XPath mode and take the current item as an argument. In each iteration of the <ForAll> loop, the current item is set to each value of the sequence.