Re: [boost] [Phoenix] review

Subject: Re: [boost] [Phoenix] review
From: Joel de Guzman (joel_at_[hidden])
Date: 2008-10-02 11:38:04

David Abrahams wrote:
> on Wed Oct 01 2008, Joel de Guzman <joel-AT-boost-consulting.com> wrote:
> 
>> I think I am convinced. Even with phx functions, the expressions
>> expressing the arguments are already "optionally lazy" anyway
>> due to C++:
>>
>>     foo(123 + 456) // foo is a phoenix function
>>
>> The expression (resulting to the argument) is eagerly evaluated.
>> Whereas:
>>
>>     foo(_1 + 456)
>>
>> it is not (eagerly evaluated).
>>
>> So it's really a case by case basis depending on what C++ can
>> evaluate eagerly.
>>
>> So, it follows that:
>>
>>     foo(123 + 456)
>>
>> can be evaluated eagerly, not only the arguments, but foo itself.
>> While:
>>
>>     foo(_1 + 456)
>>
>> can remain lazy, as usual.
> 
> It may be the right choice anyway, but keep in mind that any such
> nonuniformity limits genericity.  I think we already have that with
> Boost.Bind ("nested binds are special") but this effect is worth
> thinking about.

Yeah, I was thinking about that too. That is why I suggested to
work on this on a branch for further investigation.

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