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
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