Re: [Boost-users] gcc3.2 preprocessor concatenation or notonnegativenumbers

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2006-01-21 06:03:04

> -----Original Message-----
> From: boost-users-bounces_at_[hidden] 
> [mailto:boost-users-bounces_at_[hidden]] On Behalf Of Andy Little

> > #define CAT(a, b) PRIMITIVE_CAT(a, b)
> > #define PRIMITIVE_CAT(a, b) a ## b
> >
> > CAT(CAT(1e, -), 1)
> >
> > This works for me (as it should) on gcc3.4.4.  I can't 
> speak for gcc3.2.
> 
> Thanks Paul. It works on gcc3.2, however I need to use 
> CAT(Sign, Number)  (or Just Sign ## Number)  in the Macro too 
> and then I get a bunch of warnings
> saying:
> 
> test.cpp:25:22: warning: pasting "-" and "60" does not give a 
> valid preprocessing token

Let me see if I'm understanding you correctly...  You need to construct (e.g.)
1e-1 and also need -1 in a different spot?  In the former case, you have to
paste the pieces together in the order as specified above so that at all times
the result is a single valid preprocessing token.  In the latter case, you don't
need token-pasting at all.  Just say: Sign Number.

Regards,
Paul Mensonides