Larry Evans wrote:
On 05/06/2006 05:11 PM, dan marsden wrote:
Thanks for the feedback
Sure. And thanks for the fusion_v2 and the quick response to feedback.
No problem
However, I've got another question. I removed the value_of_impl from my code since it looks like deref_impl defines what's needed and my code ran OK. Is value_of_impl really needed to define a fusion iterator for a new struct?
value_of_impl is only used by the value_of metafunction, and is a requirement of the Fusion forward iterator concept. It is not needed in order for deref to work correctly. There is a distinction between deref and value_of: fusion::result_of::deref<It>::type - Returns the result of dereferencing It fusion::result_of::value_of<It>::type - Returns the element stored at It Now if an element of type T is stored at It then: fusion::result_of::deref<It>::type is T& fusion::result_of::value_of<It>::type is T If on the other hand an element of type T& is stored at It then: fusion::result_of::deref<It>::type is T& (as before) fusion::result_of::value_of<It>::type is T& So value_of allows us to distinguish members that are references. Hope that was what you were after. Cheers Dan