[Lazarus] How can I increment/decrement a alphanumeric value?

[silvioprog]

  Em 19/08/2010 17:26, bobby escreveu:
> Hi,
>
> I have a function for increasing HEX values, based on string 
> manipulations, not on conversion to integer and back.
> Would that be of any help?
>
> bobby 

Hi bobby,

Would you show me the function?

Here's one I received from a friend here in Brazil:

[code]
{$J+}
const
   CIncStrChars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
{$J-}

function IncStr(const AString: string): string;
var
   VCurrChar: PChar;
   I, VPos, VBackIndex: Integer;
begin
   Result := Copy(AString, 1, Length(AString));
   for I := 1 to Length(AString) do
     if Pos(AString[I], CIncStrChars) < 1 then
       raise Exception.Create('String contains an invalid character');
   if Length(AString) < 1 then
   begin
     Result := CIncStrChars[1];
     Exit;
   end;
   if Length(AString) < 2 then
   begin
     Result := Succ(AString[1]);
     Exit;
   end;
   VBackIndex := 0;
   while True do
   begin
     VCurrChar := @Result[Length(Result) - VBackIndex];
     VPos := Pos(VCurrChar^, CIncStrChars);
     if VPos = Length(CIncStrChars) then
     begin
       VCurrChar^ := CIncStrChars[1];
       if (Length(Result) - VBackIndex) <= 1 then
       begin
         Result := CIncStrChars[2] + Result;
         Break;
       end
       else
       begin
         Inc(VBackIndex);
         Continue;
       end;
     end
     else
     begin
       VCurrChar^ := CIncStrChars[VPos + 1];
       Break;
     end;
   end;
end;

Author: http://code.google.com/u/kingbizugo/
[/code]

I'm seeing with him to creating the DecStr function.

Thanks bobby. :) (and sorry for my english :p ).

Silvio Clécio