Create and populate an array of Raku objects? - raku

Question

I chose to redesign a portion of the previous code of mine, in this case, a chessboard, in Perl 6. The first two classes went well (or at least worked, I know so little that I can't speak to their correctness), but I'm stuck with the third. Here is the code:
#!/home/hsmyers/rakudo741/bin/perl6
# board.p6 - Beginnings of a PGN toolset. And place to start learning
# Perl 6/Raku.
use v6d;
#!___________________________________________________________
constant $size = 4;
class Piece {
my Str #namesOfPieces[$size] = <
white-rook white-knight white-bishop white-queen
>;
my Str #abrevsOfPieces[$size] = <
R N B Q K B N R
>;
my Str #symbolsOfPieces[$size] = <
♖ ♘ ♗ ♕ ♔ ♗ ♘ ♖
>;
my Str #codeptsOfPieces[$size] = (
"\x2656", "\x2658", "\x2657", "\x2655",
);
has Str $.name;
has Str $.abrev;
has Str $.symbol;
has Uni $.codept;
submethod BUILD( :$i ) {
$!name = #namesOfPieces[$i];
$!abrev = #abrevsOfPieces[$i];
$!symbol = #symbolsOfPieces[$i];
$!codept = #codeptsOfPieces[$i].NFC;
}
}
class Square {
my Int #colors[$size] = <
1 0 1 0 1 0 1 0
>;
my Str #names[$size] = <
a1 b1 c1 d1 e1 f1 g1 h1
>;
has Int $.color;
has Int $.index;
has Str $.name;
has Piece $.piece;
submethod BUILD( :$i ) {
$!color = #colors[$i];
$!index = $i;
$!name = #names[$i];
$!piece = Piece.new(:i($i));
}
}
class Board is Array {
}
my $p = Piece.new(:i(0));
$p.say;
my $s = Square.new(:i(0));
$s.say;
#!___________________________________________________________
my #b := Board.new(
Square.new(:i(0)),
Square.new(:i(1)),
Square.new(:i(2))
);
say #b;
say #b.WHAT;
When run at the cli, results in:
Piece.new(name => "white-rook", abrev => "R", symbol => "♖", codept => Uni.new(0x2656).NFC)
Square.new(color => IntStr.new(1, "1"), index => 0, name => "a1", piece => Piece.new(name => "white-
rook", abrev => "R", symbol => "♖", codept => Uni.new(0x2656).NFC))
[Square.new(color => IntStr.new(1, "1"), index => 0, name => "a1", piece => Piece.new(name =>
"white-rook", abrev => "R", symbol => "♖", codept => Uni.new(0x2656).NFC)) Square.new(color =>
IntStr.new(0, "0"), index => 1, name => "b1", piece => Piece.new(name => "white-knight", abrev =>
"N", symbol => "♘", codept => Uni.new(0x2658).NFC)) Square.new(color => IntStr.new(1, "1"), index =>
2, name => "c1", piece => Piece.new(name => "white-bishop", abrev => "B", symbol => "♗", codept =>
Uni.new(0x2657).NFC))]
(Board)
The Board class (empty as it is) is all that is left from my attempts so far. Amazingly (at least to me), it provides a degree of workability. It has variously had a "new" and a "BUILD," neither provided a working solution. The current approach doesn't work, considering that the actual count will be 64 and not 4.
My current notion is that I need to build an array of 64 Squares, which in turn will create the necessary pieces. I've tried to add to self with nothing working. Suggestions?

Answer 1

Inheriting from Array is probably not the best design choice here; it reveals and commits to the underlying representation of the Board, which will present refactoring challenges as the code evolves. Rather, I'd suggest that a Board has an Array of Square, which is initialized with Square objects.
Assuming the board is meant to have $size squared places, then you could do something like:
class Board {
has #.squares[$size ** 2];
method TWEAK() {
#!squares = map { Square.new(i => $_ % $size) }, ^($size ** 2);
}
}
That is, take the range from 0 up to but excluding $size squared, and then map each value into a Square instance. (We modulo the index to avoid an index out of bounds in one of the other classes.)
A 2D array may be preferable:
class Board {
has #.squares[$size;$size];
method TWEAK() {
#!squares = (map -> $i { Square.new(:$i) }, ^$size) xx $size;
}
}
Here, we map again, but this time since we're just doing one dimension we drop the modulo. The use of a named $i parameter means we can use the :$i convenience, which is short for :i($i) (there's an opportunity to do that in the code you posted also). We then take that expression producing one row, and use xx to run it $size times in order to get data for every column.
Ultimately, it will probably not be quite so simple as this; perhaps Square should take two constructor arguments, both a numeric and a letter, to form its name. That's probably best done as a map of map. Further, the initialization of Piece instances probably wants to happen in Board too; while it's been a quarter of a century since I last played chess, I'm quite sure not every square has a piece on it at the start of the game.