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: 2011-08-11 10:25:41

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 ?
>
> Yes, but I have many cases like this.
> This time it will look like this
> (the ifdef DEFINE_FOO is not needed):
>
> // my default values
> #define FOO1    foo1
> #define FOO2   foo2
> ...
> #define FOO42    foo42
>
> // optional overriding values
> # define FOO1_OVERRIDE (BOOST_PP_NIL)
> ...
> # define FOO23_OVERRIDE (BOOST_PP_NIL)
>
> // The only macro I would like to have to write
> # define FOO24_OVERRIDE (myFoo24, BOOST_PP_NIL)
>
> # define FOO25_OVERRIDE (BOOST_PP_NIL)
> ...
> # define FOO42_OVERRIDE (BOOST_PP_NIL)
>
>
> And it turns out to be simpler to write:
>
> #define FOO1_OVERRIDE    FOO1
> ...
> #define FOO23_OVERRIDE    FOO23
> #define FOO24_OVERRIDE    myFoo24
> #define FOO25_OVERRIDE    FOO25
> ...
> #define FOO42_OVERRIDE    FOO42
>
> Thanks for your help.

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.