From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: String filtering
Date: Tue, 27 Sep 2005 11:49:28 +0200
Date: 2005-09-27T11:49:31+02:00 [thread overview]
Message-ID: <1j92wa9843ylq.16j89wuqatbaj$.dlg@40tude.net> (raw)
In-Reply-To: m3mzly6fgy.fsf@rr.trudgett
On Tue, 27 Sep 2005 19:13:17 +1000, David Trudgett wrote:
> with Ada.Strings.Maps, Ada.Strings.Unbounded;
> use Ada.Strings.Maps, Ada.Strings.Unbounded;
>
> Lower_Chars : constant Character_Range := ('a', 'z');
> Upper_Chars : constant Character_Range := ('A', 'Z');
> Numer_Chars : constant Character_Range := ('0', '9');
> Alphanumeric : constant Character_Ranges
> := (Lower_Chars, Upper_Chars, Numer_Chars);
> Alphanumeric_Set : constant Character_Set := To_Set(Alphanumeric);
with Strings.Maps.Constants;
use Strings.Maps.Constants;
-- use defined there Alphanumeric_Set
> function Strip_Non_Alphanumeric
> (Str : in Unbounded_String) return Unbounded_String
> is
> New_Str : Unbounded_String
> := To_Unbounded_String(Count(Str, Alphanumeric_Set));
If you do this, then use String (1..Count (...));
> begin
> New_Str := To_Unbounded_String("");
No need for that, it is initially an empty string.
> for Char in 1 .. Length(Str) loop
> if Is_In(Element(Str, Char), Alphanumeric_Set) then
> Append(New_Str, Element(Str, Char));
> end if;
> end loop;
> return New_Str;
> end Strip_Non_Alphanumeric;
>
> Is something like that what y'all do in situations like this?
I don't.
Firstly it is not clear why characters need to be filtered out. Or better
to say, how did it happen, that you get garbage in a string? Either, you
need a character *stream* filtering, long before you get a string token out
of it, or, more realistically an error message (exception), should have
happened, for example if you take some text from a GUI widget.
Secondly, unbounded strings are rarely needed. Especially in text parsing
etc. It is quite uncommon to change a string content there. In your example
you don't do it either. You create a new string. Also both the source and
the result strings have *known* length. So you don't need unbounded strings
here. Usually, after making some trivial analysis like that you'll find out
that only 2% or so really need to be unbounded.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2005-09-27 9:49 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 [this message]
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
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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