From: Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>
Subject: Re: [newbie] simple(?) data structures
Date: Sun, 13 Jun 2004 10:12:17 +0000 (UTC)
Date: 2004-06-13T10:12:17+00:00 [thread overview]
Message-ID: <cah9a1$1qd$1@a1-hrz.uni-duisburg.de> (raw)
In-Reply-To: 2j21dlFrvu2sU1@uni-berlin.de
Roland Illig <roland.illig@gmx.de> wrote:
: tmoran@acm.org wrote:
:> Why so complicated? Why not just:
:> type Go_Board is array(integer range <>,integer range <>) of Stone;
:> This_Board : Go_Board(1 .. 19, 1 .. 19);
:> That_Board : Go_Board(1 .. 13, 1 .. 13);
:> then directly access the array instead of getStone, and use
:> This_Board'length(1) instead of getHeight and This_Board'length(2) for getWidth
:
: That's too simple. :)
:
: Seriously, I want to build abstractions using Ada,
As has been suggested, you don't need a whole lot of language
support to build the abstraction. For example, if only the size
of the board is a variable property of a Go board (once, when a
variable of type Go_Board is declared), type extensions are not
needed, neither are generics.
When there are no other properties that need to be seen from the
outside, then with a suitably defined Board_Size index type,
type Go_Board (rows, columns: Board_Size) is private;
-- ... subprogram declarations of the type Go_Board
Note that rows and columns are *constants* in a discriminated subtype
once you have declared a new board,
my_board: Go_Board(rows => 13, columns => 19);
So this is one possible equivalent of a (the outside view of)
the constructor. No variable parts of Go_Board are exposed, quite
abstract :-) You can pass my_board around, using the Go_Board
subprograms.
You are now free to place any implementation detail in the private
part, as has been demonstrated, the Go_Board subprograms will
be able to see them.
So if, for implementation, you use a 2-dimensional
array, as in you C++ example, and as in Tom Moran's example,
you can make it a part of the full type's declaration
in the private part, *and* you can use both rows, columns
and array attributes in the Go_Board subprograms.
Maybe, if there is are default values for rows and columns in
a Go board, you can use the like this:
package Go.Boards is
type Go_Board
(rows: Board_Size := 13; columns: Board_Size := 19)
is private;
-- ... subprogram declarations
private
-- ... declarations of Cell, Cell_Array, etc
type Go_Board
(rows: Board_Size := 13; columns: Board_Size := 19)
is record
cells: Cell_Array(1..rows, 1..columns);
end record;
end Go.Boards;
next prev parent reply other threads:[~2004-06-13 10:12 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-12 22:23 [newbie] simple(?) data structures Roland Illig
2004-06-12 22:52 ` Frank
2004-06-13 0:10 ` Ludovic Brenta
2004-06-13 3:13 ` Roland Illig
2004-06-13 7:59 ` Marius Amado Alves
2004-06-13 11:56 ` Ludovic Brenta
2004-06-13 14:47 ` Stephen Leake
2004-06-13 18:24 ` Jeffrey Carter
2004-06-13 0:31 ` Jeffrey Carter
2004-06-13 1:26 ` tmoran
2004-06-13 2:47 ` tmoran
2004-06-13 3:53 ` Roland Illig
2004-06-13 10:12 ` Georg Bauhaus [this message]
2004-06-13 23:32 ` Robert I. Eachus
2004-06-14 12:29 ` Georg Bauhaus
2004-06-13 4:46 ` Steve
2004-06-13 4:59 ` tmoran
2004-06-13 17:58 ` Jeffrey Carter
2004-06-16 11:08 ` Roland Illig
2004-06-16 21:05 ` Georg Bauhaus
2004-06-16 23:23 ` Roland Illig
2004-06-17 0:44 ` Jeffrey Carter
2004-06-17 12:37 ` Hyman Rosen
2004-06-17 13:11 ` Björn Persson
2004-06-18 9:55 ` Ole-Hjalmar Kristensen
2004-06-18 11:03 ` Björn Persson
2004-06-18 12:04 ` Hyman Rosen
2004-06-22 8:11 ` Ole-Hjalmar Kristensen
2004-06-18 0:20 ` David Starner
2004-06-18 5:06 ` Hyman Rosen
2004-06-18 5:47 ` Martin Krischik
2004-06-18 7:30 ` Brian May
2004-06-18 14:21 ` Larry Kilgallen
2004-06-19 19:51 ` Robert I. Eachus
2004-06-18 15:04 ` Georg Bauhaus
2004-06-19 2:02 ` James Rogers
2004-06-18 9:51 ` Ole-Hjalmar Kristensen
2004-06-27 13:12 ` Jacob Sparre Andersen
2004-06-24 0:09 ` Matthew Heaney
2004-06-24 14:50 ` Nick Roberts
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