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)? 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.
* 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. 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. If that was confusing, I assure you I'll try to explain it better in the docs. -- -Matt Calabrese