Re: [boost] [bind][phoenix] unified placeholders, yea or nay?

Subject: Re: [boost] [bind][phoenix] unified placeholders, yea or nay?
From: Thomas Heller (thom.heller_at_[hidden])
Date: 2012-05-29 03:35:26

On 05/28/2012 01:22 AM, Eric Niebler wrote:
> I'm considering taking on as a side project the unification of the bind
> and phoenix placeholders, a perennial source of confusion and annoyance.
> I hesitate before beginning because it necessarily introduces some
> complexity into boost.bind, a very small, simple, and light-weight
> library. In particular, the unification would:
>
> 1) Cause boost.bind to depend on boost.proto. (I would do what I could
> to keep that dependency as slight as possible.)
> 2) Could not be supported on all platforms; e.g. not on borland or (gcc
> <  4) where the placeholders are actually static inline functions(!).
> (Peter, is this an ODR thing?)
> 3) Would introduce Phoenix behaviors into Bind, insofar as _1 is a
> lambda such that _1(42) evaluates to 42.
>
> At this point, it's not obvious to me that the benefits outweigh the
> costs. Opinions? Peter, I'd especially like to hear your thoughts.
>
FWIW, phoenix should be able to use bind placeholder. In fact, phoenix 
can use any placeholder that specializes boost::is_placeholder. Couldn't 
we work off of that?
For example, detect in the phoenix code wether the bind header has been 
included before? Issue a warning? error?

Not sure ...