Tricky semantics of ranges & potentially numerous Phobos bugs

[H. S. Teoh]

On Tue, Oct 16, 2012 at 09:21:18PM +0200, Jonathan M Davis wrote:
[...]
> We'd probably need to add a function to the standard library (e.g.
> deepCopy) which would be defined for all built-in types and which
> user-defined types could define (with something hasDeepCopy being
> there to check for it), and then code could use that for doing deep
> copies. So again, it's possible, but it doesn't currently exist.
[...]

I think with D's compile-time introspection capabilities, it _should_ be
possible to implement a generic deepCopy template that works for any
type.

Of course, then one has to address tricky issues such as complex data
structures that have interlinking parts; a blind recursive deep-copy may
not have the desired effect (e.g., if we're deep-copying a graph and
there are multiple paths (via references) to the same node, then we
shouldn't end up with multiple copies of that node). Some care will also
need to be taken to deal with cyclic structures, etc.. And some
optimizations can probably be done to avoid copying immutable objects,
since that would be a waste of time & memory.

Probably some kind of graph traversal algorithm can be used to address
these issues, I think, perhaps with the help of an AA or two to recreate
the original linking structure in the copy.


T

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