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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Quick question regarding limited type return syntax
Date: Sat, 2 Aug 2014 09:34:04 +0200
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Xref: news.eternal-september.org comp.lang.ada:21394
Date: 2014-08-02T09:34:04+02:00
List-Id: <comp.lang.ada>

On Sat, 02 Aug 2014 10:11:59 +0300, Niklas Holsti wrote:

> More elegantly IMO, the language could allow a default initialization
> expression to be assigned in the type or subtype declaration:
> 
>    type My_Type is <type definition> := <expression>;

This suggests assigning something to the type.

(The only way to have default initialization is by having a default
constructor. Which is just same.)

BTW,

   type Integer is range ... := 0;
   subtype Positive is Integer range 1..Integer'Last;

   X : Positive; -- Oops!

[...]
> Randy's suggestion for an explicit indication that an object is
> default-initialized is an orthogonal isssue.

Yes, and it would have sense if implicitly uninitialized objects were
illegal. Unfortunately they are not.

> IMO the risk of using uninitialized variables, and the resulting
> non-deterministic bugs, is one of the major remaining holes in the
> safety of Ada.

All initialization/finalization issues are. E.g. parent's Initialize not
called. Finalization deadlock with task components. Dispatching calls
through class-wide access discriminants upon initialization/finalization.
The holes are as big as the hull...

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