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=-0.9 required=5.0 tests=BAYES_00,FORGED_GMAIL_RCVD,
	FREEMAIL_FROM autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: 103376,ed1e3e7e7d67edd4,start
X-Google-Attributes: gid103376,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news4.google.com!feeder1-2.proxad.net!proxad.net!feeder1-1.proxad.net!217.73.144.45.MISMATCH!feeder2.ecngs.de!ecngs!feeder.ecngs.de!130.59.10.21.MISMATCH!kanaga.switch.ch!switch.ch!news.grnet.gr!newsfd02.forthnet.gr!not-for-mail
From: Christos Chryssochoidis <C.Chryssochoidis@gmail.com>
Newsgroups: comp.lang.ada
Subject: Newbie's question
Date: Mon, 11 Feb 2008 16:31:34 +0200
Organization: FORTHnet S.A., Atthidon 4, GR-17671 Kalithea, Greece,
 Tel: +30 2109559000, Fax: +30 2109559333, url: http://www.forthnet.gr
Message-ID: <1202740198.391371@athprx03>
NNTP-Posting-Host: athprx03.forthnet.gr
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Trace: athprx02.forthnet.gr 1202740294 9425 193.92.150.68 (11 Feb 2008
 14:31:34 GMT)
X-Complaints-To: abuse@forthnet.gr
NNTP-Posting-Date: Mon, 11 Feb 2008 14:31:34 +0000 (UTC)
User-Agent: Thunderbird 2.0.0.9 (Macintosh/20071031)
Cache-Post-Path: newsfd02!unknown@adsl54-133.ath.forthnet.gr
Xref: g2news1.google.com comp.lang.ada:19757
Date: 2008-02-11T16:31:34+02:00
List-Id: <comp.lang.ada>

Hello,

I 'm experimenting with Ada, and I'm having trouble getting some toy 
code running. The code is the following: (hope it isn't too complicated)


-- This is a program to test passing subprograms as arguments to other 
subprograms.
-- It consists of a main program, "Test_Filter", and two nested 
subprograms: "Filter" and "Greater_Equal_3". The "Filter" subprogram 
takes as arguments an array of Integers and a function (predicate), and 
returns an array of the same type, having only those elements of the 
input array that satisfy the given predicate. For some reason that I 
can't figure out, I'm getting a "segmentation fault" when I run the 
executable. (It compiles fine.)


with Ada.Containers.Doubly_Linked_Lists;
with Ada.Text_IO;

procedure Test_Filter is

    subtype Index is Natural;
    type Int_Array is array(Index range<>) of Integer;


    function Filter(Elements : Int_Array; Predicate : not null 
access 					function(Element : Integer) return Boolean) 								return 
Int_Array  is
       package Int_Lists is new 									 
Ada.Containers.Doubly_Linked_Lists(Element_Type => Integer);
       Tmp_List : Int_Lists.List;
       Result : access Int_Array;
    begin
       for I in Elements'Range loop
          if Predicate(Elements(I)) then
             Tmp_List.Append(Elements(I));
          end if;
       end loop;

       Result := new Int_Array(1..Index(Tmp_List.Length));
   Copy_List:
       declare
          Tmp_List_Cursor : Int_Lists.Cursor := Tmp_List.First;
          I : Integer := 1;
       begin
          while Int_Lists.Has_Element(Tmp_List_Cursor) loop
             Result(I) := Int_Lists.Element(Tmp_List_Cursor);
             Tmp_List_Cursor := Int_Lists.Next(Tmp_List_Cursor);
             I := I + 1;
          end loop;
       end Copy_List;

       return Result.all;

    end Filter;

    function Greater_Equal_3(Element :Integer) return Boolean is
    begin
       if Element >= 3 then
          return True;
       else
          return False;
       end if;
    end Greater_Equal_3;


    Int_Array1 : Int_Array := Int_Array'(1,2,3,4,5);
    Int_Array2 : Int_Array(1..3);

begin
    Int_Array2 := Filter(Int_Array1, Greater_Equal_3'Access);
    for I in Int_Array1'Range loop
       Ada.Text_IO.Put_Line(Int_Array1(I)'Img);
    end loop;

    Ada.Text_IO.Put_Line("");

    for I in Int_Array2'Range loop
       Ada.Text_IO.Put_Line(Int_Array2(I)'Img);
    end loop;

end Test_Filter;


Thanks very much for any help.