From: Georg Bauhaus <rm.tsoh.plus-bug.bauhaus@maps.futureapps.de>
Subject: Re: About String
Date: Tue, 17 Jun 2008 00:02:51 +0200
Date: 2008-06-17T00:02:52+02:00 [thread overview]
Message-ID: <4856e30c$0$7535$9b4e6d93@newsspool1.arcor-online.net> (raw)
In-Reply-To: <wcc4p7txk90.fsf@shell01.TheWorld.com>
Robert A Duff wrote:
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
>
>> On Sun, 15 Jun 2008 18:06:00 -0400, Robert A Duff wrote:
>>
>>> I don't see why a loop needs a declarative part.
>>> My idea is that every statement list is a scope.
>> What is so special in statement lists? Pushing this idea further, we should
>> also conclude that any sequence of expressions is a scope. For example, an
>> aggregate:
>>
>> String'(X : constant Character := F(A(I)), 1 => X, 2 => 'a', 3 => X);
>>
>> a function call etc.
>
> Well, I suppose something like that could work, but it seems like it
> would be confusing -- how many components are there, which pieces of
> text belong to which components (or which parameters, in the function
> call case)?
>
>> [ That might be useful to overcome some silly limitations on discriminants:
>>
>> type T (S : Storage_Count) is record
>> -- Buffer : Storage_Elements_Array (0..S-1); -- This would be illegal, so
>> Buffer : Storage_Elements_Array
>> (Last : constant Storage_Offset := S-1, 0..Last);
>> end record; ]
>
> I don't see the point. Why not just make it legal (the line marked
> "This would be illegal"). Rules would be needed about when to evaluate
> that expression -- presumably on elaboration of a discriminant
> constraint, or an aggregate, or a discriminant default. I don't think
> having a name for Last makes this any easier.
>
>>>> However I find nested declare/begin/end more readable because it clearly
>>>> disambiguates between the scope of the loop and the scope of one iteration
>>>> of.
>>> I don't get it. You declare something inside a loop body, or the 'then'
>>> part of an 'if' -- it's local to that.
>> Local in which sense? There are statical nesting and dynamic execution of
>> the loop body upon iterations.
>
> The same sense as declare blocks. That is, in my "circus",
> this:
>
> ... loop
> <decls>
> <statements>
> end loop;
... loop
Get(Buffer(K));
<decls> -- depending on Buffer
<statements>
end loop;
I guess that in order to maintain the order(?)
SCOPE [DECLS] STATEMENTS END-SCOPE
we would be needing
... loop
Get(Initial(K));
begin
<decls>
<statements>
end;
end loop;
> has identical semantics to:
>
> ... loop
> declare
> <decls>
> begin
> <statements>
> end;
> end loop;
... loop
Get(Buffer(K));
declare
<decls>
begin
<statements>
end;
end loop;
Compared to the solution above, that would be an exchange
of BEGIN <-> DECLARE and the addition of a BEGIN where there
is nothing between <decls> and <statements> above.
A quick shot at syntax, what impact does this have, if any?
I'm adding a few rather artificial errors, but nevertheless:
... scope
function Foo(N: Integer := K);
return Value;
end scope;
... scope
declare
function Foo(N: Integer := K);
return Value;
begin
null;
end;
end scope;
By no more than a gut feeling I'd say that from a syntax
point of view, the omission of explicit declare blocks
adds a few more opportunities for ambiguity: RETURN is
at least not likely introducing a statement in the second
example.
next prev parent reply other threads:[~2008-06-16 22:02 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-06 17:29 About String Sébastien Morand
2008-06-07 16:18 ` Simon Wright
2008-06-07 17:01 ` Pascal Obry
2008-06-07 22:13 ` Chris Moore
2008-06-08 6:47 ` Niklas Holsti
2008-06-08 7:35 ` Dmitry A. Kazakov
2008-06-08 10:29 ` Sebastien Morand
2008-06-08 10:53 ` Dmitry A. Kazakov
2008-06-08 11:14 ` Niklas Holsti
2008-06-08 13:16 ` Dmitry A. Kazakov
2008-06-08 17:17 ` Niklas Holsti
2008-06-09 7:26 ` Dmitry A. Kazakov
2008-06-08 11:48 ` Martin
2008-06-08 13:17 ` Conditional declarations (was: About String) Dmitry A. Kazakov
2008-06-08 18:26 ` About String Chris Moore
2008-06-08 18:32 ` Robert A Duff
2008-06-08 20:51 ` Maciej Sobczak
2008-06-08 21:19 ` Robert A Duff
2008-06-09 7:14 ` Dmitry A. Kazakov
2008-06-09 9:43 ` Georg Bauhaus
2008-06-09 10:25 ` Dmitry A. Kazakov
2008-06-09 10:42 ` Sébastien Morand
2008-06-09 11:43 ` Georg Bauhaus
2008-06-09 12:03 ` Dmitry A. Kazakov
2008-06-15 19:38 ` Robert A Duff
2008-06-15 20:52 ` Dmitry A. Kazakov
2008-06-15 22:06 ` Robert A Duff
2008-06-16 8:31 ` Dmitry A. Kazakov
2008-06-16 19:17 ` Robert A Duff
2008-06-16 20:30 ` Dmitry A. Kazakov
2008-06-16 22:02 ` Georg Bauhaus [this message]
2008-06-16 23:04 ` Robert A Duff
2008-06-09 11:00 ` Georg Bauhaus
2008-06-09 14:27 ` Britt Snodgrass
2008-06-15 19:50 ` Robert A Duff
2008-06-15 19:48 ` Robert A Duff
2008-06-08 11:13 ` Simon Wright
2008-06-08 19:03 ` Sebastien Morand
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