Re: metapost question

["Meer, H. van der" <H.vanderMeer@uva.nl>]

On 21 okt. 2011, at 17:13, Peter Rolf wrote:

> Am 21.10.2011 15:05, schrieb Hans van der Meer:
>> I cannot find the answer to the following question in Knuth's Metafont book.
>> The following definition with a trailing text argument:
>> 
>> def mydef (expr a, b, c) text modifier =
>> 	if <modifier = empty>: 
> 
> Have you already tried
> 
>        if modifier = "" :
> 
> 
>> 	else:
>> 	fi
>> enddef;

I tried it now, but it doesn't work. Something like
if(TEXT4)
           ="":;fi
in the error log. No, Metapost is not happy with this construct.

>> 
>> How can I do the switch on an empty or nonempty modifier argument? It is not a string because calling its length fails with an error.
>> I must do the switch, because "fill modifier" with an empty "modifier" gives horrible results.
>> 
>> Usage would be calls like:
>>  mydef(1,2,3) withcolor green; % with modifier text
>>  mydef(1,2,3); % without modifier text

Thanks in advance.
Hans van der Meer


___________________________________________________________________________________
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://tex.aanhet.net
archive  : http://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________