From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2007-02-25 03:38:37
Matias Capeletto wrote:
> On 2/24/07, Thorsten Ottosen <thorsten.ottosen_at_[hidden]> wrote:
>
>> Matias Capeletto wrote:
>>
>>> On 2/23/07, Thorsten Ottosen <thorsten.ottosen_at_[hidden]> wrote:
>>
>>
>>>> Maybe I missed how one would use this view. How exactly (and which
page
>>>> in the documentation?)
>>>
>>>
>>>
>>> Maybe I have introduce noise here. The left view is the
bidirectional mapping
>>> view from the left, the one obtained with bm.left
>>>
>>> bimap<X,Y>::left_map_type is signature compatible with std::map<X,Y>.
>>> bimap<X,Y>::left_map_type::value_type is signature-compatible with
>>> std::pair<X,Y> and
>>> bimap<X,Y>::right_map_type::value_type is signature-compatible with
>>> std::pair<Y,X>
>>>
>>> So you can use this view or the right one with generic algorithms
that need
>>> first/second members.
>>
>>
>> I missed that. It seems like there is less to worry about then :-)
>
>
>
>> Take this example:
>>
>>
>> typedef bimap<std::string,int> results_bimap;
>> typedef results_bimap::relation position;
>>
>> results_bimap results;
>> results.insert( position("Argentina" ,1) );
>> results.insert( position("Spain" ,2) );
>> results.insert( position("Germany" ,3) );
>> results.insert( position("France" ,4) );
>>
>>
>> I could not find any documentation on direct members of
>> a bimap. Should it read results.left.insert()???
>
>
>
> No, there is some confusion here. The documentation will have to be
> changed to help grasp the essence of bimap easier. Fernando Cacciola
> has proposed some useful changes to the docs.
I looked in the reference section under bimap and it only stated
constructors and types. Have I found some old documentation on the net
somehow?
Anyway, I think I get it.
>> std::make_pair() aside, you are often forced to
>> constructing a pair object, only to copy its data once again upon
>> insertion into the map.
>
>
>
> Can you give an example?
Well, the rvalue position objects created above is a good example:
1. creare rvalue string (non-trivial) and int (trivial) arguments
2. copy string and int in position constructor
3. upon insertion, copy string and int again
So the above takes
1 constructor call
2 copy-constructor calls
per argument, Removing 1 copy-constructor call is the goal here.
-Thorsten