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

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 -- -- Dave Abrahams BoostPro Computing http://www.boostpro.com