Re: Concatenation and Characters

[Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>]

On Mon, 21 Oct 2002 09:13:53 -0500, Wes Groleau
<wesgroleau@despammed.com> wrote:

>Dmitry A.Kazakov wrote:
>> Then the language shall require them to be either initialized or 
>> *explicitly* specified as uninitialized:
>
>It already does:
>
>    O : Some_Type;             -- explicitly uninitialized
>    O : Some_Type := Default;  -- explicitly initialized
>
>It's fairly obvious which is which, and there is no third option
>that I know of.

Computer is a deterministic system, so one could claim that everything
is explicit. I would not count

O : Some_Type;

for an explicit specification that O is uninitialized.

1. In case of controlled, access, task, protected object types, O *is*
initialized.

2. In any case the syntax form for an uninitialized variable should be
no shorter than another (safer) one. For example:

O : Some_Type := <>;

or

O : Some_Type with null;

>> procedure Foo (X : out Integer := 23);
>
>That's obviously explicitly initialized.

The point is that *maybe* 

procedure Foo (X : out Integer);

should be made illegal for types which have no reasonable initial
value, because there is a possibility that X will be left unset. If it
is a desired behavior then probably it would be better to make it
clear from the specification.

>> function Foo returns Integer := 23;
>
>You're saying that instead raising program_error for failing to hit
>a return statement we should look to a default result on the spec?

Raising an exception is a run-time fault, which is usually too late. 

As for looking in spec, well, for what ever reason Ada requires that
all defaults be repeated in the bodies (:-))

---
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de