Re: [boost] [fusion] Trouble using BOOST_FUSION_ADAPT_ADT with boost::fusion::operator<

Subject: Re: [boost] [fusion] Trouble using BOOST_FUSION_ADAPT_ADT with boost::fusion::operator<
From: Joel de Guzman (joel_at_[hidden])
Date: 2012-01-17 20:14:46

On 1/18/2012 2:28 AM, GOODHART, TAYLOR wrote:
> Hi all,
> 
>  
> 
>   I'm attempting to adapt a third-party struct into a fusion sequence
> using BOOST_FUSION_ADAPT_ADT to get access to a nice operator<.
> Unfortunately compilation fails and I'm not sure if it's a bug or me
> using the library incorrectly. As best I can read the error message, it
> looks like the code is attempting to compare adt_attribute_proxy structs
> instead of the values represented by these. Below is some code that
> demonstrates the problem. Can anybody help me out?
> 

You've bumped into a limitation of proxies. Fusion adapted ADTs do
not have access to the actual L-values of the class members, but only
through get and set. As such, it actually exposes proxy elements
(adt_attribute_proxy) instead of the actual elements. The only thing
you can do with these proxies is either to get the values or set the
values:

  http://tinyurl.com/7t53h8f

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