Re: GCC 4.0 Ada.Containers Cursor danger.

[Matthew Heaney <matthewjheaney@earthlink.net>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> That's easy. Enumerate all elements in the container [i.e. define an
> order there.] Location will be that number 1..n.

There is no such thing as an "unordered" container (and here we're
really talking about sets and maps), since then there would be no way to
find anything without a linear search.  That's why we have both ordered
and hashed containers.

The "position" of an element always relative to other elements in the
container.  For an "ordered" container (Ordered_Sets, Ordered_Maps), the
position is determined by the "<" operator for elements.  For a "hashed"
container (Hashed_Sets, Hashed_Maps), the position is determined from
the hash value of the element (since that determines which bucket the
element falls into).

An iterator (either passive or active) simply enumerates elements in
their order as specified by the type of container they're in (either
sort order or bucket order).

Have you ever done any COM or DirectShow programming under Windows?  A
cursor is the same as the EnumXXX class.  (If I remember correctly, I
think Java also has something it refers to as an "enumerator".)