Re: [boost] Re : Re : Re : [preprocessor] ifdef equivalent inside a macro, is it possible?

Subject: Re: [boost] Re : Re : Re : [preprocessor] ifdef equivalent inside a macro, is it possible?
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2011-08-12 06:17:03

On 11/08/2011 21:26, Edward Diener wrote:
> On 8/11/2011 10:25 AM, Mathias Gaunard wrote:
>> On 11/08/2011 15:05, damien benoist wrote:
>>>> Is it possible for you to make the macro defined to some special value
>>>
>>>> rather than being undefined ?
>>
>> If you can list the names of all possible macros in some place, then I
>> think you can make some macro that tests if it is defined or not,
>> assuming the definition is unary.
>
> I would like to see that code. Within a macro you can test a macro for a
> value, given a limited subset of possible values, but I do not think you
> can test whether a macro is actually defined or not

If it not defined, doesn't it just expand to the name of the macro, 
which could be part of the "limited subset of possible values"?