on Thu Sep 04 2008, "Giovanni Piero Deretta" <gpderetta-AT-gmail.com> wrote:
On Thu, Sep 4, 2008 at 8:18 PM, Thorsten Ottosen <thorsten.ottosen@dezide.com> wrote:
David Abrahams skrev:
on Thu Sep 04 2008, Thorsten Ottosen <thorsten.ottosen-AT-dezide.com> wrote:
Arno Schödl skrev:
Hi, The headline pretty much says it all. Take transform iterator. When the predicate is not trivial, we also have a redundant construction of the object in the end iterator. Maybe that could be removed? best regards -Thorsten
I guess that would be restricted to forward iterators.
This has nothing to do with the wrapped iterator's type. A transform iterator currently stores a functor by value in addition to the wrapped iterator.
Have you forgotten
*--end
Yes. Sorry for the noise.
There is still some value in storing functors in optional<T>: boost.lambda expressions are not asignable, thus rendering any iterator that contains a lambda does no longer meet the requirements of Assignable of which TrivialIterator is a refinement of.
It is easy to add a wrapper around optional<T> that makes it Assignable as long as T is copy constructible (which lambdas are), so it can be used as a quick workaround for this problem.
But for that you wouldn't need the bool in optional. -- Dave Abrahams BoostPro Computing http://www.boostpro.com