[NTG-pdftex] \ifprimitive and \ifinternal/\iffeature (design proposal)

Taco Hoekwater taco at elvenkind.com
Mon Jul 4 13:32:37 CEST 2005


Hans Hagen wrote:
>> Let me propose two rather straightforward new primitives first
>> (please imagine the \ptex prefix yourself):
>>
>>   \ifprimitive <csname>
>>
>>     True if the <csname> has the same meaning as it would in initex,
>>     (but gives an error if <csname> is currently undefined).
> 
> 
> why not false instead of an error?

I proposed that because it would be slightly easier to implement,
but you need to know what you are testing anyway, so it would only
apply after e.g. \let\par\undefined. And does it really make sense to
do that to a primitive?

> in the same area, how about a primitive that marks such a primitive (or 
> maybe any macro but that may be harder to do) as being an 'if'

That is not the same problem. I will think about something like this,
but it is much harder than it appears to be at first sight.

Taco


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