Re: [boost] Re: Re: typeof

From: Joel de Guzman (joel_at_[hidden])
Date: 2004-05-03 19:53:45

Arkadiy Vertleyb wrote:
> "Brian McNamara" <lorgon_at_[hidden]> wrote
> 
> 
>>On Mon, May 03, 2004 at 09:42:16AM -0400, Arkadiy Vertleyb wrote:
>>
>>>On the other hand, since a lambda expression returns a
> 
> default-constructed
> 
>>>functor (does it? -- I am unable to verify it right now) the above
> 
> doesn't
> 
>>>make a lot of sence for Lambda...  One can just write:
>>>
>>>BOOST_TYPEOF(_1 > 15 && _2 < 20) fun;
>>
>>I don't think so.  I am pretty sure that
>>
>>   _1 < 3.3
>>and
>>   _1 < 4.4
>>
>>have the same _type_ (but they have different "double" _values_ encoded
>>in the run-time structure when constructed).
> 
> 
> Yes, thanks for correcting me.  This makes one still want to use the
> BOOST_TYPEOF_ALLOCATE macro in this case.

I'd rather want to see:

     BOOST_AUTO(fun, _1 > 15 && _2 < 20);

That would be very nifty for Spirit parsers:

     BOOST_AUTO(my_rule, int_p >> *(',' >> int_p));

I would love to incorporate this stuff into Spirit !!!
1) It would simplify grammars a lot. 2) It would give
a significant performance boost 3) It would reduce the
generated code size by as much as 80%.

See http://tinyurl.com/2wuqr and
http://tinyurl.com/2wuqr for reference.

Spirit would definitely benifit from Arkadiy's typeof. I'd like to
offer this challenge to Arkadiy. If you can easily retrofit Spirit
with a generic typeof/auto facility, I would love to make it an
integral part of the library.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net