On 11/17/2010 10:42 PM, joel falcou wrote:
On 17/11/10 22:35, Karsten Ahnert wrote:
Sure, but there is no to change the way how elements in a range are iterated. In my example, the algorithm is entirely provided by for_each with the appropriate operation.
That's not the actual problem. Bindign such thing make codes cumbersome to use in generic context where you may or may not know if a T must sue for_each or T::for_each.
The proper way to solve the original question while preserving genericity is to use tag dispatching and externally tagging each type supporting on for_each with a proper compile-time flag thanks to a proper meta-function then use it to select the implementation fo the global, free for_each function.
I think I understand. Maybe this allows the analogy to boost.range which provides an extendable layer how sequences/containers can be used in the range algorithms. Here an extendable layer is needed which allows you to change the way how thinks are iterated in for_each ( or accumulate, transform,... ), but with the additional contraint that the iteration has to be choosen according to the sequence/container.