Extended std::vector<>

[Alpar Juttner]

Based upon the idea of #462.

We could implement a wrapper around std::vector<> with the following two extra features.

• A extra permanent iterator. It has the same functionality as std::vector::iterator but remains valid even when the vector is extended by new elements. Technically, it contains a pointer to the base vector plus an index.
• An index type. In non-debug mode it is just a size_t, but in debug mode it also contains a pointer to the vector it indexes, thus operator[]() is able to check if the index indexes the right vector (and also if it is in the actual range).

Both would be safer alternatives to referencing std::vector<>'s elements by integer indices.

[Alpar Juttner]

The point is that I'm just debugging a code which uses many std::vector<>s and (integer) cross references between them and does something wrong. If we used one of the features above for cross referencing, it would immediately locate the root of the problem.

[Andras Kucsma]

Implementation of safe_vector