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

Hans Hagen pragma at wxs.nl
Mon Jul 4 15:45:01 CEST 2005

```Taco Hoekwater wrote:
> 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?

ok, we'll see, one problem that i have with errors is that oen always has to
mess around woth the moded in order to catch it

>> 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.

Understood (we've discussed such a feature before, so i already guessed that it
was complex -)

Hans

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