Re: [boost] Re: MPL usage for code generation

From: David Abrahams (dave_at_[hidden])
Date: 2003-01-23 13:09:19

Douglas Paul Gregor <gregod_at_[hidden]> writes:

> On Thu, 23 Jan 2003, David Abrahams wrote:
>
>> Douglas Paul Gregor <gregod_at_[hidden]> writes:
>>
>> > On Thu, 23 Jan 2003, David Abrahams wrote:
>> >> AFAICT it
>> >> doesn't solve the problem that Andrei was pointing at.
>> >
>> > You mean the front/pop_front issue?
>>
>> No, I mean the complexity-of-expression issue.
>
> Hmmm, I don't see how that issue applies. 

I don't know what you mean by that.  Are you saying that Andrei was
making an invalid argument?  I wouldn't agree with that.

> STL users know how to write function objects. It's not a gigantic
> leap to write function objects with a templated function call
> operator (at least, it isn't if you've already decided to play with
> template metaprogramming). The rest of the syntax is inherited from
> STL. I don't see any extra complexity here. Granted, it means
> pulling in a lot more code than Andrei's version, 

And writing a lot more code.

> but as one who has written that same bit of code approximately a
> billion times I'm ready for a simple, familiar abstraction.

Yeah, as I said I'm more comfortable with it too.

>> > Just stick your third-party iterators into sequence<> and you're all set;
>> > I'd expect that mpl::list, mpl::vector, etc. would just derive from
>> > mpl::sequence to reduce the amount of typing in the common case.
>>
>> Maybe it would be better to define namespace-scope begin(), end(),
>> et. al which can operate on STL and MPL sequences.
>
> I have two concerns with that:
>   1) begin and end are already class templates in MPL
>   2) There isn't much precedent for begin(container) and end(container);
> there is for container.begin() and container.end()

OK.  I think it would be best to start by making an experimental layer
on top of MPL in the sandbox.

-- 
                       David Abrahams
   dave_at_[hidden] * http://www.boost-consulting.com
Boost support, enhancements, training, and commercial distribution