...
  while I <= Length( S ) do
  begin
    case S[ I ] of
    '.': if not Pt then Pt := TRUE else break;
    '0'..'9': if not Pt then
                 Result := Result * 10.0 + Integer( S[ I ] ) - Integer( '0' )
              else
              begin
                D := D * 0.1;
                Result := Result + (Integer( S[ I ] ) - Integer( '0' )) * D;
              end;
    'e', 'E': begin
                Ex := Str2Int( CopyEnd( S, I + 1 ) );
                Result := Result * IntPower( 10.0, Ex );
                break;
              end;
    end;
    Inc( I );
  end;
...