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,FREEMAIL_FROM
	autolearn=unavailable autolearn_force=no version=3.4.4
X-Received: by 10.140.153.194 with SMTP id 185mr36900203qhz.1.1455099402265;
        Wed, 10 Feb 2016 02:16:42 -0800 (PST)
X-Received: by 10.182.153.2 with SMTP id vc2mr589059obb.11.1455099402204; Wed,
 10 Feb 2016 02:16:42 -0800 (PST)
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!mx02.eternal-september.org!feeder.eternal-september.org!news.glorb.com!y89no871727qge.0!news-out.google.com!l1ni8689igd.0!nntp.google.com!hb3no2944307igb.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Wed, 10 Feb 2016 02:16:41 -0800 (PST)
In-Reply-To: <7a707f07-5a82-430b-becb-5daa4f47844d@googlegroups.com>
Complaints-To: groups-abuse@google.com
Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=57.79.21.1;
 posting-account=gRqrnQkAAAAC_02ynnhqGk1VRQlve6ZG
NNTP-Posting-Host: 57.79.21.1
References: <2e3f8f3d-9247-4294-9ee7-961547674bc3@googlegroups.com>
 <7a707f07-5a82-430b-becb-5daa4f47844d@googlegroups.com>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <678d43f6-59fc-4768-b86c-9f5f43111b7b@googlegroups.com>
Subject: Re: Quick Sort in Rosetta Code
From: gautier_niouzes@hotmail.com
Injection-Date: Wed, 10 Feb 2016 10:16:42 +0000
Content-Type: text/plain; charset=ISO-8859-1
Xref: news.eternal-september.org comp.lang.ada:29476
Date: 2016-02-10T02:16:41-08:00
List-Id: <comp.lang.ada>

I did not dig too far into the fixing (the tricky thing is to avoid going out of range with indices) but here is, as an inspiration, a simplified case where the index type is integer, and this one is working (I've taken the C version to start with):

with Ada.Numerics.Float_Random; use Ada.Numerics.Float_Random;

--with Ada.Text_IO; use Ada.Text_IO;

procedure Qsort is

  type Item_array is array(Integer Range <>) of Float;

  procedure Quick_sort (a: in out Item_array) is
    n: Integer:= a'Length;
    i, j: Integer;
    p, t: Float;
  begin
    if n < 2 then
      return;
    end if;
    p := a(n / 2 + a'First);
    i:= 0;
    j:= n - 1;
    loop
      while a(i + a'First) < p loop
        i:= i + 1;
      end loop;
      while p < a(j + a'First) loop
        j:= j - 1;
      end loop;
      exit when i >= j;
      t := a(i + a'First);
      a(i + a'First) := a(j + a'First);
      a(j + a'First) := t;
      i:= i + 1;
      j:= j - 1;
    end loop;
    Quick_sort(a(a'First .. a'First + i - 1));
    Quick_sort(a(a'First + i .. a'Last));
  end;

  gen: Generator;

begin
  Reset(gen);
  for n in 1..100 loop
    for round in 1..500 loop
      declare
        start: Integer:= Integer(10.0 * (Random(gen)-0.5));
        a: Item_array(start .. start + n - 1);
      begin
        for i in a'Range loop
          a(i):= Random(gen);
        end loop;
        Quick_sort(a);
        for i in a'Range loop
          -- Put_Line(Float'Image(a(i)));
          if i > a'First and then a(i-1) > a(i) then
            raise Program_Error;  --  Buggy sorting
          end if;
        end loop;
      end;
    end loop;
  end loop;
end;
_________________________ 
Gautier's Ada programming 
http://sf.net/users/gdemont/