Hello.  I want to use associative arrays, but have a 2-d int array as my index.  so something like:

string[int[][]] chessboard;

chessboard[[0,0]] = "Rook";
chessboard[[0,1]] = "Knight";

Is this possible?  I can declare chessboard without any compiler complaints, but I haven't figured out how to assign anything to it.

Any help would be appreciated.

thanks!

dcoder

== Quote from dcoder (dcoder@devnull.com)'s article
> Hello.  I want to use associative arrays, but have a 2-d int array as my
> index.  so something like:
> string[int[][]] chessboard;
> chessboard[[0,0]] = "Rook";
> chessboard[[0,1]] = "Knight";
> Is this possible?  I can declare chessboard without any compiler complaints,
> but I haven't figured out how to assign anything to it.
> Any help would be appreciated.
> thanks!
> dcoder


Ooops, I just realized that int[someX][someY] needs to evaluate to an int, so that my statement above doesn't make any sense.

Still, is there anyway I can keep the spirit of a double index to a chessboard without having to create a Coordinate object and define relational orderings?

thanks.

dcoder.

On 22/07/2010 22:57, dcoder wrote:
> == Quote from dcoder (dcoder@devnull.com)'s article
>> Hello.  I want to use associative arrays, but have a 2-d int array as my
>> index.  so something like:
>> string[int[][]] chessboard;
>> chessboard[[0,0]] = "Rook";
>> chessboard[[0,1]] = "Knight";
>> Is this possible?  I can declare chessboard without any compiler complaints,
>> but I haven't figured out how to assign anything to it.
>> Any help would be appreciated.
>> thanks!
>> dcoder
>
>
> Ooops, I just realized that int[someX][someY] needs to evaluate to an int, so that
> my statement above doesn't make any sense.
>
> Still, is there anyway I can keep the spirit of a double index to a chessboard
> without having to create a Coordinate object and define relational orderings?
>
> thanks.
>
> dcoder.
>

How about string[][]? ;)

== Quote from awishformore (awishformore@nospam.plz)'s article

> >
> How about string[][]? ;)

yes, heheh... you are right.

I'm over thinking things.

Sorry about the noise.

On Thu, 22 Jul 2010 16:57:59 -0400, dcoder <dcoder@devenull.dev> wrote:

> == Quote from dcoder (dcoder@devnull.com)'s article
>> Hello.  I want to use associative arrays, but have a 2-d int array as my
>> index.  so something like:
>> string[int[][]] chessboard;
>> chessboard[[0,0]] = "Rook";
>> chessboard[[0,1]] = "Knight";
>> Is this possible?  I can declare chessboard without any compiler complaints,
>> but I haven't figured out how to assign anything to it.
>> Any help would be appreciated.
>> thanks!
>> dcoder
>
>
> Ooops, I just realized that int[someX][someY] needs to evaluate to an int, so that
> my statement above doesn't make any sense.
>
> Still, is there anyway I can keep the spirit of a double index to a chessboard
> without having to create a Coordinate object and define relational orderings?

This is what I think you should use:

string[int[2]]

Although, I'm not sure if you can then do something like:

chessboard[[0,1]] = "Rook";

as the [0, 1] is typed as a dynamic array.  If it does work, it may actually create [0,1] on the heap and then pass it as an int[2], which would suck.

Or, if you know how big your chessboard is (8x8 isn't a lot of memory), then:

string[8][8] chessboard;

is pretty straightforward :)

-Steve

== Quote from Steven Schveighoffer (schveiguy@yahoo.com)'s article
> This is what I think you should use:
> string[int[2]]
> Although, I'm not sure if you can then do something like:
> chessboard[[0,1]] = "Rook";
> as the [0, 1] is typed as a dynamic array.  If it does work, it may
> actually create [0,1] on the heap and then pass it as an int[2], which
> would suck.

board[[0,0]] = "Rook";

seems to work.  thanks.  But, the foreach loop looks strange.  It looks like it takes the hash value of the key:

 string[int[2]] board;

  board[[0,0]] = "Rook";
  board[[0,1]] = "Knight";

  foreach( pos, val; board) {
    writefln( "%s: %s", pos, val);
  }


Output:

2 9903680: Knight
2 9903696: Rook







> Or, if you know how big your chessboard is (8x8 isn't a lot of memory),
> then:
> string[8][8] chessboard;
> is pretty straightforward :)

Yes it is :)  Hehe....


Now, what if I wanted to do the following:


class Board {
  string[][] positions;

  this( int x, y) {
      // set the size of positions
  }
}

I want positions to internally represent a chess board, a tic tac toe board, or a Connect Four board, etc...

But, I want to fix the dimensions of the board when the board gets instantiated, so that I can have the compiler do all the work of bounds checking for me.  I can create class variables maxx, maxy and access functions that check against the variables, but I'm wondering if there's a way to make the compiler do it for you.

Is there a way?

thanks.

On 22/07/2010 23:21, dcoder wrote:
> == Quote from Steven Schveighoffer (schveiguy@yahoo.com)'s article
>> This is what I think you should use:
>> string[int[2]]
>> Although, I'm not sure if you can then do something like:
>> chessboard[[0,1]] = "Rook";
>> as the [0, 1] is typed as a dynamic array.  If it does work, it may
>> actually create [0,1] on the heap and then pass it as an int[2], which
>> would suck.
>
> board[[0,0]] = "Rook";
>
> seems to work.  thanks.  But, the foreach loop looks strange.  It looks like it
> takes the hash value of the key:
>
>   string[int[2]] board;
>
>    board[[0,0]] = "Rook";
>    board[[0,1]] = "Knight";
>
>    foreach( pos, val; board) {
>      writefln( "%s: %s", pos, val);
>    }
>
>
> Output:
>
> 2 9903680: Knight
> 2 9903696: Rook
>
>
>
>
>
>
>
>> Or, if you know how big your chessboard is (8x8 isn't a lot of memory),
>> then:
>> string[8][8] chessboard;
>> is pretty straightforward :)
>
> Yes it is :)  Hehe....
>
>
> Now, what if I wanted to do the following:
>
>
> class Board {
>    string[][] positions;
>
>    this( int x, y) {
>        // set the size of positions
>    }
> }
>
> I want positions to internally represent a chess board, a tic tac toe board, or a
> Connect Four board, etc...
>
> But, I want to fix the dimensions of the board when the board gets instantiated,
> so that I can have the compiler do all the work of bounds checking for me.  I can
> create class variables maxx, maxy and access functions that check against the
> variables, but I'm wondering if there's a way to make the compiler do it for you.
>
> Is there a way?
>
> thanks.
>

string[8][8] positions; // fixed size array

On Thu, 22 Jul 2010 17:21:15 -0400, dcoder <blah@blah.com> wrote:

> == Quote from Steven Schveighoffer (schveiguy@yahoo.com)'s article
>> This is what I think you should use:
>> string[int[2]]
>> Although, I'm not sure if you can then do something like:
>> chessboard[[0,1]] = "Rook";
>> as the [0, 1] is typed as a dynamic array.  If it does work, it may
>> actually create [0,1] on the heap and then pass it as an int[2], which
>> would suck.
>
> board[[0,0]] = "Rook";
>
> seems to work.  thanks.  But, the foreach loop looks strange.  It looks like it
> takes the hash value of the key:
>
>  string[int[2]] board;
>
>   board[[0,0]] = "Rook";
>   board[[0,1]] = "Knight";
>
>   foreach( pos, val; board) {
>     writefln( "%s: %s", pos, val);
>   }
>
>
> Output:
>
> 2 9903680: Knight
> 2 9903696: Rook

It may be represented properly inside the AA.  There are currently some bugs with AA's and using foreach.

>> Or, if you know how big your chessboard is (8x8 isn't a lot of memory),
>> then:
>> string[8][8] chessboard;
>> is pretty straightforward :)
>
> Yes it is :)  Hehe....
>
>
> Now, what if I wanted to do the following:
>
>
> class Board {
>   string[][] positions;
>
>   this( int x, y) {
>       // set the size of positions
>   }
> }
>
> I want positions to internally represent a chess board, a tic tac toe board, or a
> Connect Four board, etc...
>
> But, I want to fix the dimensions of the board when the board gets instantiated,
> so that I can have the compiler do all the work of bounds checking for me.  I can
> create class variables maxx, maxy and access functions that check against the
> variables, but I'm wondering if there's a way to make the compiler do it for you.
>
> Is there a way?

If you want it to be "compile-time-decided" but not hard-coded to 8x8:

class Board(int width, int height)
{
   string[width][height] positions;
}

Then you do:

auto brd = new Board!(8, 8);

-Steve

> 
>  string[int[2]] board;
> 
>   board[[0,0]] = "Rook";
>   board[[0,1]] = "Knight";
> 
>   foreach( pos, val; board) {
>     writefln( "%s: %s", pos, val);
>   }
> 
> 
> Output:
> 
> 2 9903680: Knight
> 2 9903696: Rook
> 

Changing the declaration to

   string[int[]] board;

makes it work (for me).
BR
/HF

dcoder wrote:
> == Quote from Steven Schveighoffer (schveiguy@yahoo.com)'s article
>> This is what I think you should use:
>> string[int[2]]
<snip>
> board[[0,0]] = "Rook";

Further to what others have said, why use strings?  There are only 12 possible chess pieces (black and white), plus blank, so probably the most efficient approach is

    char[8][8] board;

and use uppercase letters for white and lowercase for black.  This also makes it very easy to embed board positions in code, and to write/read positions to/from a file (but don't forget to validate).

But there's something else to consider.  Do you want to be able to represent:

- whose turn it is to move?
- availability of en passant capture?
- possibility of castling?  (One of my programs uses 'C' to represent a rook on which castling may still be possible, and 'R' for one on which it isn't.)

> seems to work.  thanks.  But, the foreach loop looks strange.  It looks like it
> takes the hash value of the key:
<snip>

Clearly a bug.  Need to investigate further....

Stewart.