Re: [boost] [fusion]variadic template implications for containers(was Re: Variadic Templates Redux

From: Andy Little (andy_at_[hidden])
Date: 2006-09-27 11:55:50

"David Abrahams" <dave_at_[hidden]> wrote in message
news:87wt7pjr73.fsf_at_pereiro.luannocracy.com...
> "Andy Little" <andy_at_[hidden]> writes:
>
>> "Larry Evans" <cppljevans_at_[hidden]> wrote in message
>> news:efdt92$16l$1_at_sea.gmane.org...
>>
>>> Hence, I'm wondering how a variadic template fusion vector would
>>> be implemented.  Any ideas?
>>
>> Nope. But I'm sure it will though!
>>
>> :-)
>>
>> seems a bit like ConceptGCC has broken the sound barrier don't it :-)
>
> Variadics is a separate feature from what ConceptGCC provides.  I know
> variadics are generating a lot of well-earned excitement, but think
> ConceptGCC really deserves more attention.

Sure, but  I for one have some trepidation about applying Concepts to
everything. The main issue  that worries me is that checking everything is going
to be very slow.

And I am not sure I totally agree. Although Variadic templates may be simpler,
they look to firstly actually speed up compilation, and secondly they make
tuples more like arrays. I think that means that UDT's such as those in my
physical quantities library will be much easier to use. (e.g in a matrix). And
that is important because,working with physical quantities rather than good old
doubles  really scales well. What I mean by that is that one has much better
visual cues as to what the source code is doing, what the source code is. That
is incredibly helpful as it relieves that sort of intense concentration, which
those that have programmed in assembler might know what I'm talkng about and
help you to think about the big picture and that is what I mean about
scaleability.  I think the combination of variadic templates and Fusion will go
really well with my types and probably facilitate a lot more use of UDT's.

And Variadic templates are more of something that users can use directly, though
hopefully they will get the benefit of Concepts in much more helpful error
messages.

Anyway, All these things on the horizon together with auto and decltype are
making things look up for C++ at the moment, so thanks to you Joel Alexsey,
Doug Gregor and everyone else for putting the work in to realise all this.

regards
Andy Little