On 5/29/2012 3:35 PM, Thomas Heller wrote:
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?
ADL won't pickup phx functions and operators if the placeholders are in a different namespace unless they are tinged somehow with some proto/phx. _1 + _2 will not work if _1 and _2 are both totally oblivious of proto/phx. boost::is_placeholder is not enough. Regards, -- Joel de Guzman http://www.boostpro.com http://boost-spirit.com