From: Robert A Duff <bobduff@shell01.TheWorld.com>
Subject: Re: String filtering
Date: 03 Oct 2005 13:59:56 -0400
Date: 2005-10-03T13:59:56-04:00 [thread overview]
Message-ID: <wccu0fya3c3.fsf@shell01.TheWorld.com> (raw)
In-Reply-To: 1KednYZNMNxP8NzeRVn-3A@comcast.com
tmoran@acm.org writes:
> > function Intern(Table: in out Symbol_Table; -- illegal!
> > X: String) return Symbol;
> >...
> > Tok: Token := Get_Token(Stream); [-- illegal]
> >...
> > function Get_Line(S: in out Stream) return String; -- illegal!
> Isn't that why
> function S'Input(Stream : access Ada.Streams.Root_Stream_Type'Class)
> return T;
> takes an access parameter?
Yes.
> Is it very difficult to do the same with Intern or Get_Token or Get_Line?
It's a pain to have to declare things 'aliased' all over the place.
It's a "cry wolf" thing -- 'aliased' should mean I'm making
possibly-permanent pointers to that thing. But here, we don't want
a pointer (except as a temporary by-reference parameter).
"aliased Blah'Class" means "Warning Will Robinson: this procedure might
save the pointer in a global data structure." But that's not what
S'Input is doing.
And there's some run-time overhead for access parameters -- they carry
run-time accessibility-level info with them.
Furthermore, there's (annoyingly) no way to declare a formal parameter
aliased. So you use 'access' where 'in out' should suffice, or you
declared tagged types that have no need for a tag.
Yes, there are workarounds for the lack of [in] out params on functions
-- but they have global consequences on your code.
- Bob
next prev parent reply other threads:[~2005-10-03 17:59 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-27 6:27 String filtering David Trudgett
2005-09-27 7:38 ` Jacob Sparre Andersen
2005-09-27 9:13 ` David Trudgett
2005-09-27 9:49 ` Dmitry A. Kazakov
2005-09-27 11:01 ` Martin Dowie
2005-09-27 11:12 ` Martin Dowie
2005-09-27 12:54 ` Dmitry A. Kazakov
2005-09-27 13:42 ` Martin Dowie
2005-09-27 14:24 ` Dmitry A. Kazakov
2005-09-28 0:06 ` David Trudgett
2005-09-28 8:15 ` Dmitry A. Kazakov
2005-09-28 10:39 ` David Trudgett
2005-09-28 20:55 ` Simon Wright
2005-09-28 21:53 ` Martin Dowie
2005-09-28 9:08 ` Jacob Sparre Andersen
2005-09-28 9:54 ` David Trudgett
2005-09-29 14:05 ` Georg Bauhaus
2005-10-01 19:02 ` tmoran
2005-10-02 6:38 ` David Trudgett
2005-10-02 14:11 ` Martin Dowie
2005-10-02 22:40 ` David Trudgett
2005-10-03 5:56 ` Martin Dowie
2005-10-03 10:33 ` Georg Bauhaus
2005-09-28 18:21 ` Jeffrey R. Carter
2005-09-28 21:00 ` Simon Wright
2005-09-27 11:22 ` David Trudgett
2005-09-27 11:15 ` David Trudgett
2005-09-27 13:21 ` Dmitry A. Kazakov
2005-09-27 13:43 ` Martin Dowie
2005-09-28 0:51 ` David Trudgett
2005-09-28 12:02 ` Dmitry A. Kazakov
2005-09-28 13:25 ` Marc A. Criley
2005-09-29 22:42 ` Randy Brukardt
2005-09-30 17:54 ` Robert A Duff
2005-10-02 6:57 ` Steve Whalen
2005-10-02 14:14 ` Martin Dowie
2005-10-03 1:21 ` Robert A Duff
2005-10-03 7:44 ` Jacob Sparre Andersen
2005-10-03 8:56 ` Dmitry A. Kazakov
2005-10-03 9:25 ` Jean-Pierre Rosen
2005-10-03 20:17 ` Ada Notation Jeffrey R. Carter
2005-10-03 20:41 ` Georg Bauhaus
2005-10-05 17:16 ` Andre
2005-10-05 18:23 ` Ludovic Brenta
2005-10-05 18:24 ` Jeffrey R. Carter
2005-10-04 15:13 ` brian.b.mcguinness
2005-10-04 17:00 ` String filtering Robert A Duff
2005-10-05 8:19 ` Jean-Pierre Rosen
2005-10-05 11:25 ` Robert A Duff
2005-10-04 19:47 ` Björn Persson
2005-10-05 14:14 ` Dmitry A. Kazakov
2005-10-03 10:06 ` Steve Whalen
2005-10-03 17:43 ` tmoran
2005-10-03 17:59 ` Robert A Duff [this message]
2005-10-05 23:04 ` Randy Brukardt
2005-09-27 13:52 ` Jacob Sparre Andersen
2005-09-28 1:01 ` David Trudgett
2005-09-28 1:50 ` David Trudgett
2005-09-27 14:08 ` Georg Bauhaus
2005-09-27 14:09 ` Marc A. Criley
2005-09-28 1:09 ` David Trudgett
2005-09-28 21:09 ` Simon Wright
2005-09-27 17:59 ` tmoran
2005-09-28 1:20 ` David Trudgett
2005-09-27 17:47 ` Jeffrey R. Carter
2005-09-28 1:29 ` David Trudgett
2005-09-28 18:32 ` Jeffrey R. Carter
2005-09-27 7:41 ` tmoran
2005-09-27 9:17 ` David Trudgett
2005-09-28 1:54 ` Steve
2005-09-28 2:20 ` David Trudgett
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