CODEWITHSUNDEEP
xmlfunctionxquery
ritzdiamond
ritzdiamond

Reputation: 269

Calling multiple functions within the concat function in XQuery

I need to produce a DOT graph from the following XML.

<layout>
<layout-structure>
    <layout-root id="layout-root" orientation="landscape">
        <layout-chunk id="header-text">
            <layout-leaf xref="lay-1.01"/>
            <layout-leaf xref="lay-1.02"/>
        </layout-chunk>
        <layout-leaf xref="lay-1.03"/>
                    <layout-leaf xref="lay-1.03"/>
    </layout-root>
</layout-structure>
<realization>
    <text xref="lay-1.01"/>
    <text xref="lay-1.02"/>
    <graphics xref="lay-1.03 lay-1.04"/>
</realization>
</layout>

I use the following XQuery to generate the DOT markup:

declare variable $newline := '&#10;';

declare function local:ref($root) {
  string-join((
  for $chunk in $root/layout-chunk
  return (
      concat('  "', $root/@id, '" -- "', $chunk/@id, '";', $newline),
  local:ref($chunk)
),
local:leaf($root)), "")
};

declare function local:leaf($root) {
for $leaf in $root/layout-leaf
return concat('  "', $root/@id, '" -- "', $leaf/@xref, '";', $newline)
};

let $doc := doc("layout-data.xml")/layout
let $root := $doc/layout-structure/*
return concat('graph "', $root/@id, '" { ', $newline, local:ref($root),'}')

The query above works fine and produces the following graph:

graph "layout-root" {
"layout-root" -- "header-text";
"header-text" -- "lay-1.01";
"header-text" -- "lay-1.02";
"layout-root" -- "lay-1.03";
"layout-root" -- "lay-1.04";
}

The result is shown below:

Now, what I would like to do is to assign a set of properties for each element in the DOT graph depending on their properties, defined under the realization element in the XML, as shown below:

This would, of course, require the following DOT markup:

graph "layout-root" {
"lay-1.03" [shape="box", style="filled", color="#b3c6ed"];
"lay-1.04" [shape="box", style="filled", color="#b3c6ed"]; 
"layout-root" -- "header-text";
"header-text" -- "lay-1.01";
"header-text" -- "lay-1.02";
"layout-root" -- "lay-1.03";
"layout-root" -- "lay-1.04";
}

I have written two additional variables and functions to select and write the required DOT markup:

declare variable $dotgraphics := '[shape="box", style="filled", color="#b3c6ed"]';

declare function local:gfx($doc) {
for $layout-leafs in $doc//layout-leaf
let $graphics := $doc/realization//graphics
where $graphics[contains(@xref, $layout-leafs/@xref)]
return concat($layout-leafs/@xref, ' ', $dotgraphics, ';', $newline)
};

My problem is: how do I include the function local:gfx to the working XQuery script above?

If I simply call the function *local:gfx($doc) before local:ref($root) as shown below,

return concat('graph "', $root/@id, '" { ', $newline, local:gfx($doc), $newline, local:ref($root),'}')

The query returns an error that a sequence of multiple items cannot be an argument for the concat function; how can this be fixed?

Upvotes: 1

Views: 1580

Answers (1)

Leo W&#246;rteler
Leo W&#246;rteler

Reputation: 4241

You can use fn:string-join($strings[, $separator]) for this, which takes the strings as a sequence instead. If you use $newline as the second parameter (the default is the empty string), it even inserts the line breaks for you:

string-join(('foo', 'bar', 'baz'), '&#10;')

yields

foo
bar
baz

Upvotes: 1

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