Custom metaobj object in context

Custom metaobj object in context

[Stefan Müller]

Hi,

I just tried to build my own object in metaobj but for some reason I 
cannot figure out it does not work. I tried the example from the metaobj 
manual in a tex document (it works in a metapost file):

   \startuseMPgraphic{objecttest}
     vardef newSegment@#=
       assignObj(@#,"Segment");
       ObjPoint a,b;
       ObjCode "@#b-@#a=(1cm,2cm)";
     enddef;
   \stopuseMPgraphic

When processing this with context (MkIV) I get

! Illegal parameter number in definition of \@MPG@objecttest.
<to be read again>
                    =
<argument>  vardef newSegment@##=
                                   assignObj(@##,"Segment"); ObjPoint 
a,b; Ob...
\dostartuseMPgraphic ...leuseMPgraphic {#1}{#2}{#3
                                                   }}
l.7 \stopuseMPgraphic

My first wild guess is that it has something to do with the "evil" 
@-symbol. But even if this is the case I don't know what to do to fix 
this. Any help appreciated and thank you very much in advance.

Stefan.
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Re: Custom metaobj object in context

[Hans Hagen]

On 13-7-2010 6:01, Stefan Müller wrote:
> Hi,
>
> I just tried to build my own object in metaobj but for some reason I
> cannot figure out it does not work. I tried the example from the metaobj
> manual in a tex document (it works in a metapost file):
>
> \startuseMPgraphic{objecttest}
> vardef newSegment@#=
> assignObj(@#,"Segment");
> ObjPoint a,b;
> ObjCode "@#b-@#a=(1cm,2cm)";
> enddef;
> \stopuseMPgraphic
>
> When processing this with context (MkIV) I get
>
> ! Illegal parameter number in definition of \@MPG@objecttest.
> <to be read again>
> =
> <argument> vardef newSegment@##=
> assignObj(@##,"Segment"); ObjPoint a,b; Ob...
> \dostartuseMPgraphic ...leuseMPgraphic {#1}{#2}{#3
> }}
> l.7 \stopuseMPgraphic
>
> My first wild guess is that it has something to do with the "evil"
> @-symbol. But even if this is the case I don't know what to do to fix
> this. Any help appreciated and thank you very much in advance.

no, more with # being special to tex's parser

\string# or \# will probably do


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___________________________________________________________________________________

Re: Custom metaobj object in context

[Stefan Müller]

On 13.07.2010 21:03, Hans Hagen wrote:
> On 13-7-2010 6:01, Stefan Müller wrote:
>> Hi,
>>
>> I just tried to build my own object in metaobj but for some reason I
>> cannot figure out it does not work. I tried the example from the metaobj
>> manual in a tex document (it works in a metapost file):
>>
>> \startuseMPgraphic{objecttest}
>> vardef newSegment@#=
>> assignObj(@#,"Segment");
>> ObjPoint a,b;
>> ObjCode "@#b-@#a=(1cm,2cm)";
>> enddef;
>> \stopuseMPgraphic
>>
>> When processing this with context (MkIV) I get
>>
>> ! Illegal parameter number in definition of \@MPG@objecttest.
>> <to be read again>
>> =
>> <argument> vardef newSegment@##=
>> assignObj(@##,"Segment"); ObjPoint a,b; Ob...
>> \dostartuseMPgraphic ...leuseMPgraphic {#1}{#2}{#3
>> }}
>> l.7 \stopuseMPgraphic
>>
>> My first wild guess is that it has something to do with the "evil"
>> @-symbol. But even if this is the case I don't know what to do to fix
>> this. Any help appreciated and thank you very much in advance.
>
> no, more with # being special to tex's parser
>
> \string# or \# will probably do

Thank you Hans for the fast answer. Adding \string in front of every # 
led to basically the same error message (only difference: "@\sting ##" 
instead of "@##"). When using \# instead of # in the vardef the small 
example from above works (even with \placefigure added). But there is 
still a problem:

   \starttext
     \startuseMPgraphic{objecttest}
       vardef newSegment@\#=
         assignObj(@\#,"Segment");
         ObjPoint a,b;
         ObjCode "@\#b-@\#a=(1cm,2cm)";
       enddef;
       newSegment.s; % create an instance
     \stopuseMPgraphic

     \placefigure[here][fig:objecttest]{My 
object}{\useMPgraphic{objecttest}}
   \stoptext

now produces the metapost error

! Isolated expression.
<to be read again>
                    (
newSegment->begingroup.assignObj(
 
(SUFFIX2),"Segment");ObjPoint.a,b;ObjCode"@...
<to be read again>
                    ;
<*> ... "@#b-@#a=(1cm,2cm)"; enddef; newSegment.s;

Without \placefigure there is no error at all. (Maybe then metapost 
doesn't even run?) And I again have no clue what's going on. Thanks for 
your help in advance.

Stefan.
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___________________________________________________________________________________

Re: Custom metaobj object in context

[Aditya Mahajan]

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On Wed, Jul 14, 2010 at 7:16 AM, Stefan Müller <warrence.stm@gmx.de> wrote:

> On 13.07.2010 21:03, Hans Hagen wrote:
>
>> On 13-7-2010 6:01, Stefan Müller wrote:
>>
>>> Hi,
>>>
>>> I just tried to build my own object in metaobj but for some reason I
>>> cannot figure out it does not work. I tried the example from the metaobj
>>> manual in a tex document (it works in a metapost file):
>>>
>>> \startuseMPgraphic{objecttest}
>>> vardef newSegment@#=
>>> assignObj(@#,"Segment");
>>> ObjPoint a,b;
>>> ObjCode "@#b-@#a=(1cm,2cm)";
>>> enddef;
>>> \stopuseMPgraphic
>>>
>>
Can you post a complete metapost file that gives some output.I tried the
following mp file:
input metaobj;
vardef newSegment@#=
assignObj(@#,"Segment");
ObjPoint a,b;
ObjCode "@#b-@#a=(1cm,2cm)";
enddef;
beginfig(1) ;
newSegment.s; % create an instance
endfig ;
end;

but running it through metapost gives me an empty file:
%!PS
%%BoundingBox: 0 0 0 0
%%HiResBoundingBox: 0 0 0 0
%%Creator: MetaPost 1.208
%%CreationDate: 2010.07.15:0119
%%Pages: 1
%%BeginProlog
%%EndProlog
%%Page: 1 1
showpage
%%EOF

Aditya

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___________________________________________________________________________________

Re: Custom metaobj object in context

[Stefan Müller]

On 15.07.2010 07:21, Aditya Mahajan wrote:
 > Can you post a complete metapost file that gives some output.I tried the
 > following mp file:
 > input metaobj;

Now that's a good start... It didn't occur to me, that I need to "input 
metaobj" as in your example. Thank you very much for that hint. My 
examples now work in ConTeXt with

   \startMPinclusions
     input metaobj;
   \stopMPinclusions

I assume posting the complete example is needless now. Possibly, it 
might have been a good idea to drop a note on this in the metaobj 
manual, as it is not working without that input line.

Stefan
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