I think I have the problem nailed down to the fact that in the comparison:
something >= -1234
the parser in question separates the minus in the negative number into a separate child node, apart from the digits; witness the errormessage in the log below.
Changing the number  -1234 in the arithmetic expression to number("-1234") (mind the quotes) does give a correctly evaluated expression.

Still, I am baffled by the fact that in arithmetic expressions positive and negative numbers are treated differently in the filtering operation.

Hans van der Meer


On 29 Apr 2016, at 15:04, Meer, Hans van der <H.vanderMeer@uva.nl<mailto:H.vanderMeer@uva.nl>> wrote:

Here is a minimal example showing that even a number as -1 is not correctly handled by the lpath[selection]-code.
I really am convinced that not handling negative numbers should qualify as a mistake.

Hans van der Meer


% failure of negative number comparison.
\startxmlsetups demo:numberfail
\xmlsetsetup{#1}{root|node}{demo:numberfail:*}
\stopxmlsetups
\xmlregisterdocumentsetup{demo}{demo:numberfail}
\startxmlsetups demo:numberfail:root
@atta >= 1:\crlf
\xmlfilter{#1}{/[number(@atta) >= 1]/command(demo:numberfail:node)}
\blank
@atta >= -1:\crlf
\xmlfilter{#1}{/[number(@atta) >= -1]/command(demo:numberfail:node)}
\xmlfilter{#1}{/[number(@atta) >= number(-1)]/command(demo:numberfail:node)}
\stopxmlsetups
\startxmlsetups demo:numberfail:node
node: attribute atta = \xmlatt{#1}{atta}\crlf
\stopxmlsetups
\startbuffer[numberfail]
<root>
<node atta="2"/>
<node atta="3"/>
</root>
\stopbuffer
\starttext
\xmlprocessbuffer{demo}{numberfail}{}
the error from \type{\xmlfilter{#1}{/[number(@atta) >= -1]/command(demo:numberfail:node)}}:
\starttyping
xml > lpath > error in expression: number(@atta) >= -1 => expr.number((ll.at<http://ll.at/> and ll.at<http://ll.at/>['atta'])) >= expr.child(ll,'-')1
\stoptyping

the error from \type{\xmlfilter{#1}{/[number(@atta) >= number(-1)]/command(demo:numberfail:node)}}:
\starttyping
xml > lpath > error in expression: number(@atta) >= number(-1) => expr.number((ll.at<http://ll.at/> and ll.at<http://ll.at/>['atta'])) >= expr.number(expr.child(ll,'-')1)
\stoptyping
\stoptext

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