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

Subject: Re: [Boost-users] [optional] boost improvement over std::map, the default initialization requirement
From: Emil Dotchevski (emil_at_[hidden])
Date: 2010-07-18 14:47:02

On Sun, Jul 18, 2010 at 4:48 AM, Dave Abrahams <dave.abrahams_at_[hidden]> wrote:
> On Sunday, July 18, 2010, alfC <alfredo.correa_at_[hidden]> wrote:
>> Hi,
>>  The STL has an implementation of std::map<T1, T2>. 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