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Subject: Re: Your wish list for Ada 202X
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Date: 2014-04-22T02:30:17-06:00
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On 22-Apr-14 02:02, Dmitry A. Kazakov wrote:
> But there should be no Open operation at all.

Why not?
It seems to me that Open could be ideal for some object, like say an 
object representing flood-gates, or an internally used operation for an 
"e-mail reader", or dozens of other things (perhaps file processing 
[e.g. Get_File_List, Filter, Open as basic 'operations' of the processor]).

> The object must be functional  in each its state. Open is not an
> operation it is a part of the object's constructor.

Again, see the above. -- I realize you're talking about _files_, but 
there's many more things that could need an 'open' than just files. 
{Moreover, 'open' might even be hidden in the implementation.}

> This is another language problem that Ada forces you to introduce Open,
> which adds unusable object states (not yet opened object), must be
> overridden (but there is no way to spell that requirement), must call
> to the parent's Open (but. again, no way to ensure that).

Not entirely true; with pre/post conditions, and perhaps type-invariants 
you can prohibit such states from being entered (which will result in an 
exception).