Re: Common sense...

[Jeffrey Carter <jrcarter@acm.org>]

"chris.danx" wrote:
> 
> "Jeffrey Carter" <jrcarter@acm.org> wrote in message
> news:3D25E607.E59E11E2@acm.org...
> > Deleting nodes from an iterator is erroneous and should raise an
> > exception.
> 
> ok but how would you enforce that.  Just not support it?  That's no bother
> as the iterators aren't written yet.

The PragmAda Reusable Components' list components' iterators will raise
an exception (Invalid_Position) if the client-supplied action deletes
the current node. This is a consequence of assigning a unique ID to each
list, marking each Position and node with the ID of the associated list,
and invalidating the ID when a node is deleted.

A simpler approach might be to add a Boolean field to the list structure
that the iterator sets True before it begins traversing the list, and
sets False when the iteration is finished. Deletion would then check
this field first, and raise the exception if it is True.

-- 
Jeff Carter
"If you think you got a nasty taunting this time,
you ain't heard nothing yet!"
Monty Python and the Holy Grail