On 6/11/2010 12:27 PM, David Abrahams wrote:
At Fri, 11 Jun 2010 12:12:27 -0400,
That gives us an opportunity to add a new feature to Phoenix: default capture modes. I could see something like:
ref[ phoenix-lambda-expression ]
makes default capture by-ref, and
val[ phoenix-lambda-expression ]
I would be cautious about emulating C++0x lambdas. I'm not sure yet that they don't suck.
They suck, but not for this reason. ;-)
makes it by-val. Under the hood, Phoenix would actually be storing every captured variable both by value and by reference.
!! Sounds expensive.
The plan has always been to make capture-by-value the default. Saving off a reference as well is free.
why not perfect forwarding?
Because it's too expensive to simulate in C++98.
Oh, I meant for 0x. Be cautious, also, about designing for C++98 at the expense of a good 0x interface.
Agreed in principle, but I don't think we have much choice at this point. We want Phoenix to be usable today. How long will it before we can reasonably assume everyone doing C++ has variadics and rvalue refs? A long time, I think. As a compromise, we can put the variadic/rvalue ref implementation on a switch and let users opt in if they have the features and don't care about portability. -- Eric Niebler BoostPro Computing http://www.boostpro.com