From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,386228a37afe967f
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2003-07-21 01:49:43 PST
Path: 
 archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.icl.net!newsfeed.fjserv.net!newsfeed.freenet.de!newsfeed.r-kom.de!fu-berlin.de!uni-berlin.de!tar-alcarin.cbb-automation.DE!not-for-mail
From: Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Computer Language Shootout
Date: Mon, 21 Jul 2003 10:53:46 +0200
Message-ID: <vp9nhv8ju4t5kjrvdtd3sp3qgt59nu31tt@4ax.com>
References: <n54tgvgugor0ag2qsv97t9mf9sn9rr542i@4ax.com>
 <slrnbgtckk.54b.randhol+abuse@kiuk0152.chembio.ntnu.no>
 <1ec946d1.0307150715.4ba69f85@posting.google.com> <3F149243.80304@attbi.com>
 <gE4Ra.103343$Io.8883476@newsread2.prod.itd.earthlink.net>
 <3F15930C.2070907@attbi.com>
 <slrnbhcrk3.jt.randhol+abuse@kiuk0152.chembio.ntnu.no>
 <evacnf433pJrU4uiXTWJgA@gbronline.com> <mqm6fb.pn3.ln@skymaster>
 <wcc65m0omev.fsf@shell01.TheWorld.com> <ubrvrwmwt.fsf@wanadoo.fr>
NNTP-Posting-Host: tar-alcarin.cbb-automation.de (212.79.194.111)
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Trace: news.uni-berlin.de 1058777382 14828671 212.79.194.111 (16 [77047])
X-Newsreader: Forte Agent 1.8/32.548
Xref: archiver1.google.com comp.lang.ada:40537
Date: 2003-07-21T10:53:46+02:00
List-Id: <comp.lang.ada>

On 18 Jul 2003 23:22:10 +0200, Pascal Obry <p.obry@wanadoo.fr> wrote:

>
>Robert A Duff <bobduff@shell01.TheWorld.com> writes:
>
>> "Jean-Pierre Rosen" <rosen@adalog.fr> writes:
>> 
>> > This one reads a line with no length limit:
>> > 
>> > function Get_Line return String is
>  [...]
>>
>> Too bad this was not included in Text_IO itself.  It would save
>> beginners a lot of trouble.  Sigh.
>
>But this approach can use a lot of stack space and become very slow.
>Returning an unconstraint object on the stack has a cost.

I don't think that the following, heap-based, version could be much
faster:

Increment : constant := 500;

type String_Ptr is access all String;
procedure Free is
   new Ada.Unchecked_Deallocation (String, String_Ptr);

procedure Read_Line
          (  Line   : in out String_Ptr;
             Length : out Natural
             )  is
   Size : Natural;
begin
   Get_Line (Line.all, Size);
   Length := Size;
   while Size = Line'Last loop
      declare
         Old_Line : String_Ptr := Line;
      begin
         Line := new String'(Old_Line.all & (1..Increment => ' '));
         Free (Old_Line);
      end;
      Get_Line (Line (Length + 1..Line'Last), Size);
      Length := Length + Size;
   end loop;   
end Read_Line;

used as:

   Line    : String_Ptr := new String'(1..Increment => ' ');
   Length  : Natural;
begin is
   Read_Line (Line, Length);
   ...
   Free (Line);
exception
   when others =>
      Free (Line);
      raise;
   
Though it should remove exponential growth [at cost of nasty
pointers].

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