Re: [Boost-users] [optional] boost improvement over std::map, the default initialization requirement

On Sun, Jul 18, 2010 at 4:48 AM, Dave Abrahams wrote:

On Sunday, July 18, 2010, alfC wrote:

...

Hi,  The STL has an implementation of std::map. It has some designs drawbacks in my opinion. For example, the fact that T2 has to have a default copy constructor. Even if for T2, by design, doesn't make sense to have a copy constructor.

The problem boils down to the fact that, in the STL design, if an key element of the map is referenced with the operator[] and it doesn't exist then an 'empty' (default) object T2 is created. In my opinion this feature is independent of the other features of a map. For example if the element doesn't exists and the context is not assignment then it could give an exception.

Easy solution:  use find and insert instead of operator[]. HTH

I haven't done any timings but isn't lower_bound+insert potentially better because you can then pass the iterator from lower_bound to insert as a hint? Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode