Re: [Boost-users] [phoenix] function with reference implementation

Subject: Re: [Boost-users] [phoenix] function with reference implementation
From: Joel de Guzman (joel_at_[hidden])
Date: 2010-09-10 20:47:08

On 9/11/10 8:31 AM, alfC wrote:
>
>
> On Sep 10, 4:36 pm, Joel de Guzman<j..._at_[hidden]>  wrote:
>> On 9/11/10 4:37 AM, alfC wrote:
>>
>>
>>
>>> I noticed that in some contexts I have both the object class and the
>>> corresponding phoenix function
>>
>>>     class impl;
>>>     ...
>>
>>>     impl f_impl;
>>>     boost::phoenix::function<impl>    f(f_impl);
>>
>>> now to avoid the copying I could use:
>>
>>>     boost::phoenix::function<impl&>    f(f_impl);
>>
>>> which works. Although
>>>     boost::phoenix::function<impl const&>    f(f_impl); //doesn't work.
>>> (error below)
>>
>>> Is there any problem with using references at all, in the first place?
>>
>> I'm not sure. Could you provide a minimal cpp file I can try?
>
> Yes, see below. Althougth now that I made this example I realize that
> the underlying object implementation is copied many times anyway (at
> least 4 times in the example), I guess during the building up of the
> expression template. [The final objective was to make an object
> function that not only evaluates but also is able to take expression
> and build expression templates].

Here's my suggestion: write a proxy function object that holds
the target function object by reference, pointer, or boost.ref
and use that to wrap your phoenix function.

HTH,

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