Re: [boost] Interest in a container which can hold multiple data types?

Subject: Re: [boost] Interest in a container which can hold multiple data types?
From: Boris Rasin (boris_at_[hidden])
Date: 2015-05-05 05:21:55

On 5/5/2015 9:31 AM, Thijs (M.A.) van den Berg wrote:
>>> tuple_vector<Point, Line, Rectangle, Circle> shapes;
>>> shapes.push_back(Point{1.0, 1.0} );
>> This is neat, but it' not quite the same thing. Unlike std::vector<boost::any>, your tuple_vector does not organize objects into strictly linear arrangement. Using your example, there is no way to draw shapes in the order they were inserted into container.
>>
> Good point! So it loses overall ordering, only preservers it at the type level. The reason is that objects gets stored in linear memory per type.

One could conceivably add another internal container to maintain overall 
index. But than again, is such tuple_vector<Point, Line, Rectangle, 
Circle> really better than std::vector<boost::variant<Point, Line, 
Rectangle, Circle>>? It would use less memory per object when some 
stored types are smaller than others, and in some circumstances these 
savings would exceed overhead of multiple internal containers and an 
additional index container. Any other advantages?