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From: "Alex Mentis" <foo@invalid.invalid>
Newsgroups: comp.lang.ada
Subject: Re: index check failure - constraint error
Date: Fri, 1 Apr 2011 11:27:30 +0000 (UTC)
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Date: 2011-04-01T11:27:30+00:00
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tonyg wrote:

> On Apr 1, 11:53�am, tonyg <tonytheg...@gmail.com> wrote:
> > I'm getting a constraint error and I cannot see why...
> > 
> > � �function String_To_Integer (The_String : String) return Integer
> > is � � � String_Length : Integer := The_String'length;
> > � � � Return_Value : Integer := 0;
> > � � � subtype Number_Character �is character range '0'..'9';
> > � �begin
> > � � � � Int_Io.Put(String_Length);
> > � � � Ada.Text_IO.Put_Line (The_String);
> > � � � if String_Length > 0 then
> > � � � for count in 1..String_Length loop
> > � � � � �case The_String(count) is
> > � � � � � � when Number_Character =>
> > � � � � � � � �Return_Value := Return_Value +
> > � � � � � � � � �((Character'pos(The_String(count)) - 48) *
> > (10**(count-1)));
> > � � � � � � when others =>
> > � � � � � � � �raise Conversion_Error_Exception;
> > � � � � �end case;
> > � � � � �end loop;
> > � � � else
> > � � � � �Return_Value := 0;
> > � � � end if;
> > 
> > � � � return Return_Value;
> > 
> > � �end String_To_Integer;
> > 
> > I checked to see there was a string going in and it had a length.
> > The actual error was 'index check failure' but as far as I can see
> > everything is present and correct. Can anyone see what it is ?
> 
> The index check failure occurred at
> 
>   case The_String(count) is
> 
> btw


Any particular reason you aren't using the Ada-provided Get procedure
that converts a String to an Integer? It operates just like the usual
Get procedure, consuming all Integer-valid characters and stopping when
it gets to a non-digit, but you can make it detect and throw your
constraint with something like this:

with Ada.Text_Io, Ada.Integer_Text_Io;
use  Ada.Text_Io;

Procedure Main is
   
   Conversion_Error_Exception : exception;   
   
   Input1 : String := "123";
   Input2 : String := "1E3";
   Input3 : String := "12ab3";
   My_Int : Integer;
   Length : Positive;
   
begin
      
   Ada.Integer_Text_Io.Get (Input1, My_Int, Length);
   if Length /= Input1'Length then
      raise Conversion_Error_Exception;
   else
      Ada.Integer_Text_Io.Put (My_Int, 0);
      New_Line;
   end if;
   
   Ada.Integer_Text_Io.Get (Input2, My_Int, Length);
   if Length /= Input2'Length then
      raise Conversion_Error_Exception;
   else
      Ada.Integer_Text_Io.Put (My_Int, 0);
      New_Line;
   end if;
   
   Ada.Integer_Text_Io.Get (Input3, My_Int, Length);
   if Length /= Input3'Length then
      raise Conversion_Error_Exception;
   else
      Ada.Integer_Text_Io.Put (My_Int, 0);
      New_Line;
   end if;   
   
end Main;