Re: How come Ada isn't more popular?

On Wed, 07 Feb 2007 08:54:58 +0100, Maciej Sobczak wrote:

Dmitry A. Kazakov wrote:

For handling cycles there are weak pointers.

Not only. If you have cycles, then you'd better rethink the design.
The difference is between a) graph treated as a mesh (or mess) of nodes
which "own" each other and b) graph treated as a collection of nodes.
The former might have ownership cycles between nodes, but not the
latter, where ownership is an acyclic relation between graph and nodes.
I agree that this kind of restructuring is not always possible, but for
me it is conceptually cleaner and worth trying from the beginning.

I would say that in all cases all references within it should be
non-controlled. The argumentation could go as follows:

A controlled reference (subject of GC) expresses the life-time relation
"not before me." [*] This relation is obviously transitive (due to nature
of time). Ergo, there cannot be any cycles, per definition.

From this stand point I would claim that a cycle of controlled references
manifests either a bug or a design problem. That a buggy program continues
to function as-if there were no bug, barely should be attributed as an
advantage of GC systems.

-----------------
* One cannot say that the relation is "before or together with me,"
because nothing can happen simultaneous. Even if two [collection] actions A
and B could happen concurrently, then A and B were independent, thus there
could be no any time constraint between them.

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
.

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