Re: [boost] [phoenix] not playing nice with other libs

Subject: Re: [boost] [phoenix] not playing nice with other libs
From: Cromwell Enage (sponage_at_[hidden])
Date: 2011-05-02 15:17:11

--- On Mon, 5/2/11, Thomas Heller wrote:
> On Mon, May 2, 2011 at 12:54 PM, Eric Niebler wrote:
> > Phoenix is changing the following fundamental constants:
> >
> >  BOOST_PROTO_MAX_ARITY
> >  BOOST_MPL_LIMIT_METAFUNCTION_ARITY
> >  BOOST_PROTO_MAX_LOGICAL_ARITY
> >  BOOST_RESULT_OF_NUM_ARGS
> >
> > IMO, Phoenix shouldn't be touching these.  It should
> > work as best it can with the default values.  Users who
> > are so inclined can change them.
> 
> Eric,
> This problem is well known.  As of now I have no clue how
> to fix it properly.

What I usually do instead of changing the values of existing constants is to start each header file with, for each fundamental constant used, what I'll dub a "constant guard":

#if BOOST_PP_LESS(BOOST_PROTO_MAX_ARITY, SOME_MINIMUM_VALUE)
#error Please set BOOST_PROTO_MAX_ARITY to SOME_MINIMUM_VALUE or higher
#endif

IOW, I'm just passing the buck to the library user or to the application developer.

HTH,
Cromwell D. Enage