Access current element in xmlsetsetup via xml.expressions

Access current element in xmlsetsetup via xml.expressions

[achim]

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Hello,

I'm trying to build an xmlsetsetup with an own lua function. XML in MKIV
says on pg. 33:

You can also use normal Lua functions as long as you make sure that you pass
the right arguments.

There are a few predefined variables available inside such functions.

list table the list of matches

l number the current index in the list of matches

ll element the current element that matched

order number the position of the root of the path

 

But I can't figure out how to get access to list, ll etc.

My MWE (only for testing the access, is always true):

 

\startbuffer[text]

<para>Dies ist <inline style="sup">ein</inline> xxx<inline
style="sub">zwei</inline> noch ein <inline style="sup">sup</inline>
Test<inline style="sub">sub</inline></para>

\stopbuffer

%\enabletrackers[xml.parse,xml.path]

 

\startluacode

  function xml.expressions.nextnodeatt(e)

                inspect(e)

                inspect(ll)

                return('sub')

  end

\stopluacode

 

\startxmlsetups xml:textsetups

    \xmlsetsetup{#1}{*}{+}

    \xmlsetsetup{#1}{para}{xml:*}

 
\xmlsetsetup{#1}{inline[@style='sup'][xml.expressions.nextnodeatt(ll)=='sub'
]}{xml:sub}

\stopxmlsetups

 

\xmlregistersetup{xml:textsetups}

 

\startxmlsetups xml:para

    \xmlflush{#1}\par

\stopxmlsetups

 

\startxmlsetups xml:sub

    \color[red]{\xmlflush{#1}}

\stopxmlsetups

 

 

\starttext

    \xmlprocessbuffer{main}{text}{}

\stoptext

 

Thanks in advance,

Achim


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Re: Access current element in xmlsetsetup via xml.expressions

[Taco Hoekwater]

> On 1 Oct 2019, at 21:24, achim@jander.de wrote:
> 
> Hello,
> I’m trying to build an xmlsetsetup with an own lua function. XML in MKIV says on pg. 33:
> You can also use normal Lua functions as long as you make sure that you pass the right arguments.
> There are a few predefined variables available inside such functions.
> list table the list of matches
> l number the current index in the list of matches
> ll element the current element that matched
> order number the position of the root of the path
>  
> But I can’t figure out how to get access to list, ll etc.

Neither can I :(

Taco

> My MWE (only for testing the access, is always true):
>  
> \startbuffer[text]
> <para>Dies ist <inline style="sup">ein</inline> xxx<inline style="sub">zwei</inline> noch ein <inline style="sup">sup</inline> Test<inline style="sub">sub</inline></para>
> \stopbuffer
> %\enabletrackers[xml.parse,xml.path]
>  
> \startluacode
>   function xml.expressions.nextnodeatt(e)
>                 inspect(e)
>                 inspect(ll)
>                 return('sub')
>   end
> \stopluacode
>  
> \startxmlsetups xml:textsetups
>     \xmlsetsetup{#1}{*}{+}
>     \xmlsetsetup{#1}{para}{xml:*}
>     \xmlsetsetup{#1}{inline[@style='sup'][xml.expressions.nextnodeatt(ll)=='sub']}{xml:sub}
> \stopxmlsetups
>  
> \xmlregistersetup{xml:textsetups}
>  
> \startxmlsetups xml:para
>     \xmlflush{#1}\par
> \stopxmlsetups
>  
> \startxmlsetups xml:sub
>     \color[red]{\xmlflush{#1}}
> \stopxmlsetups
>  
>  
> \starttext
>     \xmlprocessbuffer{main}{text}{}
> \stoptext
>  
> Thanks in advance,
> Achim
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________

Taco Hoekwater
Elvenkind BV




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___________________________________________________________________________________

Re: Access current element in xmlsetsetup via xml.expressions

[mf]

The answer is in lxml-lpt.lua, where built-in expressions are defined.
You need a good knowledge of LPEG that i miss.

Some built-in expressions get the current element as first argument, 
like count() or child() (lines 1300-1307 of lxml-lpt.lua):

expressions.child = function(e,pattern)
     return applylpath(e,pattern) -- todo: cache
end

expressions.count = function(e,pattern) -- what if pattern == empty or nil
     local collected = applylpath(e,pattern) -- todo: cache
     return pattern and (collected and #collected) or 0
end

Some other expressions use a template that passes the "list", "ll", "l" 
and "order" arguments you find cited in the XML manual §4.1 "Path 
expressions - Expressions and filters".
These are the lines 738-743 in lxml-lpt.lua:

local template_e = [[
     local expr = xml.expressions
     return function(list,ll,l,order)
         return %s
     end
]]

That template is used by the function that registers a new expression 
(lines 807-812 in lxml-lpt.lua):

local function register_expression(expression)
     local converted = lpegmatch(converter,expression)
     local runner = load(format(template_e,converted))
     runner = (runner and runner()) or function() 
errorrunner_e(expression,converted) end
     return { kind = "expression", expression = expression, converted = 
converted, evaluator = runner }
end

Anyway i could not find a way to define an expression with a function 
like this:

xml.expressions.myexpr( ... )

that gets access to those arguments.

The only arguments it gets are the ones you specify in your LPATH 
expressions; AFAIK they are attributes values -- with the @attr syntax 
-- and strings.

Best wishes,
Massi
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___________________________________________________________________________________

Re: Access current element in xmlsetsetup via xml.expressions

[Hans Hagen]

On 10/2/2019 12:32 PM, mf wrote:
> The answer is in lxml-lpt.lua, where built-in expressions are defined.
> You need a good knowledge of LPEG that i miss.
> 
> Some built-in expressions get the current element as first argument, 
> like count() or child() (lines 1300-1307 of lxml-lpt.lua):
> 
> expressions.child = function(e,pattern)
>      return applylpath(e,pattern) -- todo: cache
> end
> 
> expressions.count = function(e,pattern) -- what if pattern == empty or nil
>      local collected = applylpath(e,pattern) -- todo: cache
>      return pattern and (collected and #collected) or 0
> end
> 
> Some other expressions use a template that passes the "list", "ll", "l" 
> and "order" arguments you find cited in the XML manual §4.1 "Path 
> expressions - Expressions and filters".
> These are the lines 738-743 in lxml-lpt.lua:
> 
> local template_e = [[
>      local expr = xml.expressions
>      return function(list,ll,l,order)
>          return %s
>      end
> ]]
> 
> That template is used by the function that registers a new expression 
> (lines 807-812 in lxml-lpt.lua):
> 
> local function register_expression(expression)
>      local converted = lpegmatch(converter,expression)
>      local runner = load(format(template_e,converted))
>      runner = (runner and runner()) or function() 
> errorrunner_e(expression,converted) end
>      return { kind = "expression", expression = expression, converted = 
> converted, evaluator = runner }
> end
> 
> Anyway i could not find a way to define an expression with a function 
> like this:
> 
> xml.expressions.myexpr( ... )
> 
> that gets access to those arguments.
> 
> The only arguments it gets are the ones you specify in your LPATH 
> expressions; AFAIK they are attributes values -- with the @attr syntax 
> -- and strings.
Live is complex isn't it? The problem, is that we also support the 
normal path expressions which in retrospect maybe was a bad idea ... 
better be explicit. Strings without quotes are actually intercepted as 
element references (just like the @ is).

So, I added a few extra accessors:

\startbuffer[text]
<para>
     A <inline style="sup">sup 1</inline>
     B <inline style="sub">sub 1</inline>
     C <inline style="sup">sup 2</inline>
     D <inline style="sub">sub 2</inline>
     E <inline style="sup">sup 3</inline>
     F <inline style="sup">sup 4</inline>
     G <inline style="sup">sup 5</inline>
     H <inline style="sub">sub 5</inline>
     I <inline style="sup">sup 6</inline>
</para>
\stopbuffer

\startluacode
     function xml.expressions.MyCheck(list,position,what)
      -- print("list",    list)
      -- print("position",position)
      -- print("what",    what)
         local n = list[position+1]
         return n and n.at.style == what
     end
\stopluacode

\enabletrackers[lxml.*]

\startxmlsetups xml:textsetups

     \xmlsetsetup{#1}{para|inline}{xml:*}

     % with a helper:

%     \xmlsetsetup{#1}{inline[@style='sup' and 
MyCheck(list(),position(),"sub")]}{xml:supsub}
%     \xmlsetsetup{#1}{inline[@style='sup' and 
MyCheck(list(),position(),"sup")]}{xml:supsup}

     % rather verbose, we *need* to use ['at'] and not .at

%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
list()[position()+1]['at']['style']=='sub')]}{xml:supsub}
%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
list()[position()+1]['at']['style']=='sup')]}{xml:supsup}

     % also ok

%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
attribute(list()[position()+1],'style')=='sub')]}{xml:supsub}
%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
attribute(list()[position()+1],'style')=='sup')]}{xml:supsup}

     % direct checking

%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
attribute(list()[position()+1],'style','sub'))]}{xml:supsub}
%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
attribute(list()[position()+1],'style','sup'))]}{xml:supsup}

     % shorter

     \xmlsetsetup{#1}{inline[@style='sup' and 
(attribute(list()[position()+1],'style','sub'))]}{xml:supsub}
     \xmlsetsetup{#1}{inline[@style='sup' and 
(attribute(list()[position()+1],'style','sup'))]}{xml:supsup}
\stopxmlsetups

\xmlregistersetup{xml:textsetups}

\startxmlsetups xml:para
     \xmlflush{#1}\par
\stopxmlsetups

\startxmlsetups xml:supsub
     \color[red]{\xmlflush{#1}}
\stopxmlsetups

\startxmlsetups xml:supsup
     \color[blue]{\xmlflush{#1}}
\stopxmlsetups

\startxmlsetups xml:inline
     \color[green]{\xmlflush{#1}}
\stopxmlsetups

\starttext
     \xmlprocessbuffer{main}{text}{}
\stoptext

In the next beta. Now, who is going to wikify this ...

Hans

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
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___________________________________________________________________________________

Re: Access current element in xmlsetsetup via xml.expressions

[achim]

Dear Hans,
that is really great. Thank's a lot.  Ill check the next beta and try to wikifiy (maybe I need further help for that)

Achim

-----Ursprüngliche Nachricht-----
Von: ntg-context <ntg-context-bounces@ntg.nl> Im Auftrag von Hans Hagen
Gesendet: Mittwoch, 2. Oktober 2019 18:53
An: mailing list for ConTeXt users <ntg-context@ntg.nl>; mf <massifr@fastwebnet.it>
Betreff: Re: [NTG-context] Access current element in xmlsetsetup via xml.expressions

On 10/2/2019 12:32 PM, mf wrote:
> The answer is in lxml-lpt.lua, where built-in expressions are defined.
> You need a good knowledge of LPEG that i miss.
> 
> Some built-in expressions get the current element as first argument, 
> like count() or child() (lines 1300-1307 of lxml-lpt.lua):
> 
> expressions.child = function(e,pattern)
>      return applylpath(e,pattern) -- todo: cache end
> 
> expressions.count = function(e,pattern) -- what if pattern == empty or 
> nil
>      local collected = applylpath(e,pattern) -- todo: cache
>      return pattern and (collected and #collected) or 0 end
> 
> Some other expressions use a template that passes the "list", "ll", "l" 
> and "order" arguments you find cited in the XML manual §4.1 "Path 
> expressions - Expressions and filters".
> These are the lines 738-743 in lxml-lpt.lua:
> 
> local template_e = [[
>      local expr = xml.expressions
>      return function(list,ll,l,order)
>          return %s
>      end
> ]]
> 
> That template is used by the function that registers a new expression 
> (lines 807-812 in lxml-lpt.lua):
> 
> local function register_expression(expression)
>      local converted = lpegmatch(converter,expression)
>      local runner = load(format(template_e,converted))
>      runner = (runner and runner()) or function()
> errorrunner_e(expression,converted) end
>      return { kind = "expression", expression = expression, converted 
> = converted, evaluator = runner } end
> 
> Anyway i could not find a way to define an expression with a function 
> like this:
> 
> xml.expressions.myexpr( ... )
> 
> that gets access to those arguments.
> 
> The only arguments it gets are the ones you specify in your LPATH 
> expressions; AFAIK they are attributes values -- with the @attr syntax
> -- and strings.
Live is complex isn't it? The problem, is that we also support the normal path expressions which in retrospect maybe was a bad idea ... 
better be explicit. Strings without quotes are actually intercepted as element references (just like the @ is).

So, I added a few extra accessors:

\startbuffer[text]
<para>
     A <inline style="sup">sup 1</inline>
     B <inline style="sub">sub 1</inline>
     C <inline style="sup">sup 2</inline>
     D <inline style="sub">sub 2</inline>
     E <inline style="sup">sup 3</inline>
     F <inline style="sup">sup 4</inline>
     G <inline style="sup">sup 5</inline>
     H <inline style="sub">sub 5</inline>
     I <inline style="sup">sup 6</inline> </para> \stopbuffer

\startluacode
     function xml.expressions.MyCheck(list,position,what)
      -- print("list",    list)
      -- print("position",position)
      -- print("what",    what)
         local n = list[position+1]
         return n and n.at.style == what
     end
\stopluacode

\enabletrackers[lxml.*]

\startxmlsetups xml:textsetups

     \xmlsetsetup{#1}{para|inline}{xml:*}

     % with a helper:

%     \xmlsetsetup{#1}{inline[@style='sup' and 
MyCheck(list(),position(),"sub")]}{xml:supsub}
%     \xmlsetsetup{#1}{inline[@style='sup' and 
MyCheck(list(),position(),"sup")]}{xml:supsup}

     % rather verbose, we *need* to use ['at'] and not .at

%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
list()[position()+1]['at']['style']=='sub')]}{xml:supsub}
%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
list()[position()+1]['at']['style']=='sup')]}{xml:supsup}

     % also ok

%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
attribute(list()[position()+1],'style')=='sub')]}{xml:supsub}
%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
attribute(list()[position()+1],'style')=='sup')]}{xml:supsup}

     % direct checking

%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
attribute(list()[position()+1],'style','sub'))]}{xml:supsub}
%     \xmlsetsetup{#1}{inline[@style='sup' and (position() < last() and 
attribute(list()[position()+1],'style','sup'))]}{xml:supsup}

     % shorter

     \xmlsetsetup{#1}{inline[@style='sup' and (attribute(list()[position()+1],'style','sub'))]}{xml:supsub}
     \xmlsetsetup{#1}{inline[@style='sup' and (attribute(list()[position()+1],'style','sup'))]}{xml:supsup}
\stopxmlsetups

\xmlregistersetup{xml:textsetups}

\startxmlsetups xml:para
     \xmlflush{#1}\par
\stopxmlsetups

\startxmlsetups xml:supsub
     \color[red]{\xmlflush{#1}}
\stopxmlsetups

\startxmlsetups xml:supsup
     \color[blue]{\xmlflush{#1}}
\stopxmlsetups

\startxmlsetups xml:inline
     \color[green]{\xmlflush{#1}}
\stopxmlsetups

\starttext
     \xmlprocessbuffer{main}{text}{}
\stoptext

In the next beta. Now, who is going to wikify this ...

Hans

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://context.aanhet.net archive  : https://bitbucket.org/phg/context-mirror/commits/
wiki     : http://contextgarden.net
___________________________________________________________________________________

___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
archive  : https://bitbucket.org/phg/context-mirror/commits/
wiki     : http://contextgarden.net
___________________________________________________________________________________