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

Subject: [boost] [bind][phoenix] unified placeholders, yea or nay?
From: Eric Niebler (eric_at_[hidden])
Date: 2012-05-27 19:22:56

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.

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com