On Fri, Apr 9, 2010 at 3:35 PM, Eric Niebler <eric@boostpro.com> wrote:
On 4/8/2010 4:25 PM, Daniel Walker wrote:
On Thu, Apr 8, 2010 at 6:51 PM, Eric Niebler <eric@boostpro.com> wrote:
On 4/8/2010 3:07 PM, Daniel James wrote:
This reverts the fixes for:
Support for boost.lambda.
This bug is invalid to begin with. Lambda should be changed to support the TR1 result_of protocol (which is standard), not the other way around.
No, the result_of in this patch can detect the type of any callable object, including those from boost.lambda, in contexts where the type of the call expression is complete. Now, lambda users who would like to query the type of lambda function objects should use their compiler's std::result_of, if it implements any draft of the standard from the past 2 years, or simply roll their own.
Hi Daniel,
IIUC the fix here for Boost.Lambda was to implement the c++0x result_of on supporting compilers. That's fine -- as long as you accept that a decltype-based result_of is a safe substitute for the TR1 result_of, which I don't.
That's fine, but safe is a relative term. Other users might have a higher tolerance for the risks of being an early adopter. I think boost can accommodate both sorts of users. If you compile with -std=c++0x, you already know your moving into a new world, and I think boost should be there waiting.
My point above was that this bug should have been closed "Invalid" because it's not a result_of problem. The problem is that Lambda doesn't support the TR1 result_of protocol. <snip>
This is a problem in c++98 and I agree with your solution for c++98 (and the long-term path from Proto to Phoenix to Lambda). But in c++0x the TR1 result_of protocol is superseded. It just so happens that fixing the "bug" of boost/lambda compatibility is trivial in c++0x, even though it's complicated in c++98. This patch fixes the bug in c++0x. Daniel Walker