From: Hans Hagen <j.hagen@xs4all.nl>
To: Geert Verhaag <verhaaggchm@ziggo.nl>,
mailing list for ConTeXt users <ntg-context@ntg.nl>
Subject: Re: Request for xml.filter explanation!
Date: Thu, 11 Apr 2019 17:33:18 +0200 [thread overview]
Message-ID: <abb18f9e-7f07-e10b-ace8-5ce6fd7c191b@xs4all.nl> (raw)
In-Reply-To: <52377958-b72e-12aa-8f52-b3280670b842@ziggo.nl>
On 4/10/2019 9:27 PM, Geert Verhaag wrote:
> Hi,
>
> I've the following xml file:
>
> *<?xml version='1.0' standalone='yes?>
>
> <content>
> <object mid="a">
> <text>a paragraph of text</text>
> <value>40.2</value>
> </object>
> <object mid="b">
> <text>another paragraph of text</text>
> <value>10.7</value>
> </object>
> <object mid="c">
> <text>still another paragraph!</text>
> <value>20.5</value>
> </object>
> </content>*
>
> And want to calculate the total value of all the objects:
>
> like so:
>
> *\startxmlsetups xml:example:base
> \xmlsetsetup{#1}{content|object}{xml:example:*}
> \stopxmlsetups
>
> \xmlregisterdocumentsetup{example}{xml:example:base}
>
> \startxmlsetups xml:example:content
> totalvalue: \xmlfunction{#1}{totalvalue}
> \xmlflush{#1} \endgraf
> \stopxmlsetups
>
> \startxmlsetups xml:example:object
> attribute : \xmlatt{#1}{mid} \par
> \stopxmlsetups
>
> % LUA
>
> \startluacode
> function xml.functions.totalvalue(root)
> local score = 0
> for e in xml.collected(root,"/object") do
> tex.write('Okay!')
> --score = score + xml.filter(e,"xml:///value/number()") or 0
> end
> tex.write(score)
> end
> \stopluacode
>
> \starttext
>
> \xmlprocessfile{example}{content.xml}{}
>
> \stoptext*
>
> *
> *
>
> When I run this example I get:
>
> *totalvalue: Okay!Okay!Okay!0 attribute : a
> attribute : b
> attribute : c*
>
> That looks allright!
>
> But when I incorporate the line:
>
> *score = score + xml.filter(e,"xml:///value/number()") or 0*
>
> the following Lua error is thrown:
> **
>
> *! LuaTeX error [string "\directlua "]:5: attempt to perform arithmetic
> on a nil value*
>
> Has anybody any idea what I'm doing wrong here? The manual
> *xml-mkiv.pdf* doesn't give any clue about this!
\startluacode
function xml.functions.totalvalue(root)
local score = 0
for e in xml.collected(root,"/object/value") do
score = score + tonumber(xml.text(e)) or 0
end
context(score)
end
\stopluacode
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prev parent reply other threads:[~2019-04-11 15:33 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-10 19:27 Geert Verhaag
2019-04-11 15:33 ` Hans Hagen [this message]
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