Re: [boost] [typeof] while we're at it...

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2006-01-29 12:11:42

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of Tobias Schwinger

> Paul Mensonides wrote:
> > BOOST_PP_IF(
> >     n,
> >     BOOST_PP_TUPLE_EAT,
> >     BOOST_PP_TUPLE_REM
> > )(1)( EXPENSIVE_MACRO_INVOCATION() )
> > 
> > ...where EXPENSIVE_MACRO_INVOCATION() is only invoked if 'n' is 0.
> 
> Guessing from the overtone of your comment it would be better to say
> 
>    BOOST_PP_IF(n, BOOST_PP_TUPLE_EAT(0), EXPENSIVE_MACRO_INVOCATION)()
> 
> to be on the safe side with less compliant preprocessors. Correct?

Yes.  It's also just better.  Sorry, it is getting late in the morning here, and
I haven't slept yet.

> ---
> 
>    #define MACRO(x) x
>    MACRO(BOOST_PP_EMPTY())
> 
> BTW. is this special case safe (theoretically and 
> practically, that is)?

On a good preprocessor, it's safe.  Broken preprocessors tend to allow empty
arguments anyway, so it should be safe there too.

Regards,
Paul Mensonides