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From: "tmoran@acm.org" <tmoran@acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Newbie question
Date: Thu, 12 Mar 2009 18:59:14 -0700 (PDT)
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Date: 2009-03-12T18:59:14-07:00
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On Mar 12, 5:29=A0am, Olivier Scalbert <olivier.scalb...@algosyn.com>
wrote:
> Hello,
>
> I start learning Ada and I try to define types for a chess engine.
>
> I have create some "obvious" types:
>
> =A0 =A0 =A0type Color_T is (White, Black);
>
> =A0 =A0 =A0type PieceType_T is (Pawn, Knight, Bishop, Rook, Queen, King);
>
> =A0 =A0 =A0type Piece_T is record
> =A0 =A0 =A0 =A0 =A0Color: Color_T;
> =A0 =A0 =A0 =A0 =A0PieceType: PieceType_T;
> =A0 =A0 =A0end record;
>
> Now, I want to create an array of 64 squares representing the chess
> board. A square should contain nothing or a Piece_T
>
> I have tried:
>
> =A0 =A0 =A0type Board_T is array(1..64) of Piece_T;
>
> But I can not have an empty square !
>
> What is the best way of doing that ?
>
> Thanks,
>
> Olivier

A piece in a game is not so much a physical object as a characteristic
of a particular square.  You don't want to say for instance
  Synod : array(1 .. 5) of (Color=3D>White, Kind=3D>Bishop);
  ...
  Board(G,3) :=3D Synod(4);
So how about
  type Occupants is (Empty, Black_King, Black_Queen, Black_Bishop,
                   .... White_King, White_Queen, .... White_Pawn);
  subtype Blacks is Occupants range (Black King .. Black_Pawn);
  subtype Whites is Occupants range (White King .. White_Pawn);
  Board : array(Files, Ranks) of Occupants;
then your code can say things like
  if Board(G,4) in Whites then ...
  if Board(G, 5) =3D Black_King and Board(G,6) =3D Empty then ...