Re: Struggling with startuseMPgraphic and string argument!

[Hans Hagen <j.hagen@xs4all.nl>]

On 9/16/2020 4:32 PM, Geert Verhaag wrote:
> Hi,
> 
> I'm trying to pass a string argument value to an MPgraphic but it 
> doesn't seem to work:
> 
> Tried the following:
> 
> \startuseMPgraphic{name}{lbl}
>    pair a ; a := (3cm,3cm) ;label.top("\MPvariable{lbl}",a) ;
> \stopuseMPgraphic
> 
> \starttext
>    \useMPgraphic{name}{lbl=1}
> \stoptext
> 
> The above works as expected!
> 
> But the following doesn't:
> 
> \startuseMPgraphic{name}{lbl}
>    pair a ; a := (3cm,3cm) ;label.top("\MPvariable{lbl}",a) ;
> \stopuseMPgraphic
> 
> \starttext
>    \useMPgraphic{name}{lbl=abc}
> \stoptext
> 
> It yields:
> 
>   1 \startuseMPgraphic{name}{lbl}
>   2       pair a ; a := (3cm,3cm) ;label.top("\MPvariable{lbl}",a) ;
>   3     \stopuseMPgraphic
>   4
>   5     %\startuseMPgraphic{name}fill fullcircle scaled 200pt withcolor 
> .625yellow ;\stopuseMPgraphic
>   6
>   7     \starttext
>   8      Example:
>   9 >>    \useMPgraphic{name}{lbl=abc}
> 10     \stoptext
> 11
> 
> <to be read again>
> a
> \m_meta_current_variable a-a
>                              bc
> <argument> ... \hbox {\scratchdimen \m_meta_current_variable
>                                                    sp}\ifzeropt \wd 
> \b_meta_v...
> \secondoftwoarguments #1#2b-#2
> 
> \9>>1 #1,2-\meta_prepare_instance_variable {#1}
> \syst_helpers_do_process_comm...
> \syst_helpers_do_process_comma_list ...rgument #1,
>                                                    ]\relax \global 
> \advance \...
> ...
> l.9   \useMPgraphic{name}{lbl=abc}
> 
> So it seems that only numbers can be passed not character strings! Why 
> is that? Is there a possibility to achieve this functionality?
magic:

\startuseMPgraphic{name}{s::lbl}
   pair a ; a := (3cm,3cm) ;label.top("\MPvariable{lbl}",a) ;
\stopuseMPgraphic

\starttext
   \useMPgraphic{name}{lbl=abc}
   \useMPgraphic{name}{lbl=def}
\stoptext

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                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
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