Giovanni Piero Deretta wrote:
Also note that Boost.Lambda can't be used here. A Boost.Lambda functor is not Assignable.
Yes, that is very unfortunate and I think it should be fixed.
I saw that oven uses a special wrapper to make boost.lambda objects copiable. What does it exactly do?
As you guess, the wrapper uses Boost.Optional. It's rather simple: http://tinyurl.com/2nvw59
The wrapper I use simply does a placement new in its assignment operator. This is very exception unsafe, but I presume that most (all?) lambda objects won't throw on copy constructor. Using boost.optional would give the basic exception safetly, but it does increase the size of the wrapper.
I'm not sure. Boost.Optional also seems to use placement-new. Anyway, Boost.Optional seems fundamental, because Boost.Lambda functors are not DefaultConstructible, which ForwardIterator requires. Regards, -- Shunsuke Sogame