[xsl] Key lookup without context.

["peter verhaar" <peter.verhaar1@xxxxxxxxx>]

Hello,

I have a 'context-free' function which does a key() lookup. However,
saxon is complaining:

SXWN9009: Cannot select a node here: the context item is undefined

Question: How can I say: "Start a key lookup from the root of the file"?

I tried select="\\key('myKey'...."  but this didn't work.

So I have:

<xsl:key name="myKey" match="books/book/...." use="..."/>

<xsl:function name="...." as="xs:double">
 <xsl:param name="input"/>
    <xsl:for-each select="key('myKey',$input)">
        processing goes here
    </xsl:for-each>
</xsl:function>