On Mon, Oct 18, 2010 at 11:14 PM, David Abrahams <dave@boostpro.com> wrote:
At Mon, 18 Oct 2010 22:17:25 +0800, Dean Michael Berris wrote:
Does it help the argument for a change if a macro can do the job?
Maybe; I don't know.
Worth a shot then. :)
I mean, what can a preprocessor macro do that the compiler can't built-in from the front-end? :D
“Look ahead” without processing the code semantically.
Ah. Hmmm... that's a tough one. But then how does the compiler do something like deduce the return type of a lambda? auto f = [](int x) { return x * 2; } Shouldn't the same mechanism be available in normal function declarations even without the computation of the return type? I would love to be able to write functions that look like: auto f(int x) { return x * 2; } This does mean though that the auto function without a trailing return type cannot be 'extern' -- and would most likely behave like a template function. Anyway, I think that suggestion wasn't well thought out but I'm throwing it out there anyway.
“Implementability” is not a question of whether it can be implemented at all, but of whether it can be implemented reasonably within the architecture of existing compilers. If it requires a ground-up redesign of some major compiler, it's effectively unimplementable.
Right, because that would mean C++0x is not an incremental change to C++03. Understood.
I also doubt the committee members weren't paying attention. The standard is already huge as it is and diving deep into the details (and the aesthetics) of the implementation of one specific feature is time and effort consuming.
I really hope it's not yet beyond repair at this point. :)
I wouldn't hold out much hope that this can happen for C++0x, unless you can convince some national body that it's so important that the standard should be rejected if they don't get it. That's what happened for exception-safety. But that sort of thing is rare.
Yeah, well in the worst case Boost would have a library pending for review (I assume) that does offer the ability to write one-liner functions with trailing return types through a preprocessor macro. Not that bad IMO, maybe it can be made part of C++1x. :) -- Dean Michael Berris deanberris.com