At Sun, 17 Oct 2010 14:16:51 -0400, Matt Calabrese wrote:
On Sun, Oct 17, 2010 at 5:32 AM, David Abrahams <dave@boostpro.com> wrote:
At Fri, 15 Oct 2010 19:22:16 -0400, Matt Calabrese wrote:
To see how the macro is used go here: http://codepaste.net/4u34ma
Nice!! Now are you ready to write BOOST_PARAMETER_AUTO_FUNCTION? :-)
Ha. You know, I actually considered using Boost.Parameter internally for its type template features before opting for just specializations, but for some reason I never even thought of trying to support Boost.Paramter functions. Perhaps for release 10 :p
On Sun, Oct 17, 2010 at 5:32 AM, David Abrahams <dave@boostpro.com> wrote:
Questions
* The "keywords" are getting a bit long. Could you think of shorter names? Super bonus for finding a way to make them highlight distinctively ;-)
I could certainly change requires_expression to requires_expr or anything else that makes sense. I'm not tied to anything in particular
When you say highlight, do you mean try to reuse more C++ keywords so they highlight in IDEs, something like I do with "return" (and I guess "requires" if C++ were to eventually get concepts)?
Something like that.
I could use "break" instead of "end". "explicit" might make sense for explicitly specifying the return type as opposed to "result_type", though I feel like the latter may be more clear. Maybe I could use "if" instead of "requires". If you have any other suggestions, let me know. I'm all for something like that as long as the keywords make sense.
Worth trying, all of them.
* is it possible to make all return types lazily computed, so there's no need for lazy_result_type? I'm not saying I see how to do this, but you might :-)
Definitely. I could make it work like mpl::apply (I think that's a feature of apply unless I'm mistaken) and just use ::type if its there, otherwise use the type itself.
But then, how would you return something that happens to have a nested ::type? Wrap it in identity?
In the code right now I implement result_type with lazy_result_type anyway by wrapping it in mpl::identity.
* What is (end) and where is it needed?
Ah, yeah, I should have been more clear on that. Perhaps I'll make a more descriptive error message if you misuse it. "end" is required when you want to end a function header such as to either separate the declaration from the implementation, or to use the macro with a multi-line function. You can only use it if you have explicitly specified a return type. You can't use it after a "return", but rather, you use it instead of return. If you declare a function with "end" you must also define it with "end", otherwise your declaration will be for a different function than your definition (ouch!). One reason why you may wish to use "end" even when you're not separating declaration from implementation is if you are using BOOST_AUTO_FUNCTION only for "requires" or "requires_expression" rather than automatic return type deduction, and it's difficult to convert your function template to a 1-liner.
Can't you just detect whether "return" was used, and if not, sythesize the "end" internally? -- Dave Abrahams BoostPro Computing http://www.boostpro.com