Square extension type

CHANGELOG.md

@@ -1,3 +1,9 @@
+## 0.8.0
+
+### Breaking changes:
+- `Square` is now an extension type.
+- Introduce `File` and `Rank` types.
+
 ## 0.7.1
 
 - Add Piece.kind, Role.letter and Role.uppercaseLetter getters.

benchmark/dartchess_benchmark.dart

@@ -1,6 +1,6 @@
 import 'package:benchmark/benchmark.dart';
 import 'package:dartchess/dartchess.dart';
-import 'dart:io';
+import 'dart:io' as io;
 
 void main() {
   benchmark('make fen from initial position', () {
@@ -37,19 +37,15 @@ void main() {
     legalMovesPos.legalMoves.length;
   });
 
-  benchmark('algebraic legal moves', () {
-    algebraicLegalMoves(legalMovesPos);
-  });
-
   benchmark('parsePgn - kasparov-deep-blue', () {
     final String data =
-        File('./data/kasparov-deep-blue-1997.pgn').readAsStringSync();
+        io.File('./data/kasparov-deep-blue-1997.pgn').readAsStringSync();
 
     PgnGame.parseMultiGamePgn(data);
   });
 
   final game = PgnGame.parsePgn(
-      File('./data/lichess-bullet-game.pgn').readAsStringSync());
+      io.File('./data/lichess-bullet-game.pgn').readAsStringSync());
   benchmark('makePgn', () {
     game.makePgn();
   });

example/dartchess_example.dart

@@ -6,12 +6,10 @@ void main() {
       'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1');
   final pos = Chess.fromSetup(setup);
 
-  // Generate legal moves in algebraic notation
-  final legalMoves = algebraicLegalMoves(pos);
+  // Generate legal moves
+  assert(pos.legalMoves.length == 16);
 
-  assert(legalMoves['e2']!.length == 2);
-
-  const move = NormalMove(from: 12, to: 28);
+  const move = NormalMove(from: Square.e2, to: Square.e4);
 
   assert(pos.isLegal(move));
 

lib/src/attacks.dart

@@ -1,22 +1,18 @@
 import './square_set.dart';
-import './utils.dart';
 import './models.dart';
 
 /// Gets squares attacked or defended by a king on [Square].
 SquareSet kingAttacks(Square square) {
-  assert(square >= 0 && square < 64);
   return _kingAttacks[square];
 }
 
 /// Gets squares attacked or defended by a knight on [Square].
 SquareSet knightAttacks(Square square) {
-  assert(square >= 0 && square < 64);
   return _knightAttacks[square];
 }
 
 /// Gets squares attacked or defended by a pawn of the given [Side] on [Square].
 SquareSet pawnAttacks(Side side, Square square) {
-  assert(square >= 0 && square < 64);
   return _pawnAttacks[side]![square];
 }
 
@@ -89,18 +85,16 @@ SquareSet _computeRange(Square square, List<int> deltas) {
   SquareSet range = SquareSet.empty;
   for (final delta in deltas) {
     final sq = square + delta;
-    if (0 <= sq &&
-        sq < 64 &&
-        (squareFile(square) - squareFile(sq)).abs() <= 2) {
-      range = range.withSquare(sq);
+    if (0 <= sq && sq < 64 && (square.file - Square(sq).file).abs() <= 2) {
+      range = range.withSquare(Square(sq));
     }
   }
   return range;
 }
 
 List<T> _tabulate<T>(T Function(Square square) f) {
   final List<T> table = [];
-  for (Square square = 0; square < 64; square++) {
+  for (final square in Square.values) {
     table.insert(square, f(square));
   }
   return table;
@@ -116,18 +110,18 @@ final _pawnAttacks = {
 };
 
 final _fileRange =
-    _tabulate((sq) => SquareSet.fromFile(squareFile(sq)).withoutSquare(sq));
+    _tabulate((sq) => SquareSet.fromFile(sq.file).withoutSquare(sq));
 final _rankRange =
-    _tabulate((sq) => SquareSet.fromRank(squareRank(sq)).withoutSquare(sq));
+    _tabulate((sq) => SquareSet.fromRank(sq.rank).withoutSquare(sq));
 final _diagRange = _tabulate((sq) {
-  final shift = 8 * (squareRank(sq) - squareFile(sq));
+  final shift = 8 * (sq.rank - sq.file);
   return (shift >= 0
           ? SquareSet.diagonal.shl(shift)
           : SquareSet.diagonal.shr(-shift))
       .withoutSquare(sq);
 });
 final _antiDiagRange = _tabulate((sq) {
-  final shift = 8 * (squareRank(sq) + squareFile(sq) - 7);
+  final shift = 8 * (sq.rank + sq.file - 7);
   return (shift >= 0
           ? SquareSet.antidiagonal.shl(shift)
           : SquareSet.antidiagonal.shr(-shift))

lib/src/board.dart

@@ -124,7 +124,7 @@ class Board {
           file += code - 48;
         } else {
           if (file >= 8 || rank < 0) throw const FenError('ERR_BOARD');
-          final square = file + rank * 8;
+          final square = Square(file + rank * 8);
           final promoted = i + 1 < boardFen.length && boardFen[i + 1] == '~';
           final piece = _charToPiece(c, promoted);
           if (piece == null) throw const FenError('ERR_BOARD');
@@ -147,7 +147,7 @@ class Board {
     int empty = 0;
     for (int rank = 7; rank >= 0; rank--) {
       for (int file = 0; file < 8; file++) {
-        final square = file + rank * 8;
+        final square = Square(file + rank * 8);
         final piece = pieceAt(square);
         if (piece == null) {
           empty++;

lib/src/constants.dart

@@ -1,6 +1,3 @@
-const kFileNames = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'];
-const kRankNames = ['1', '2', '3', '4', '5', '6', '7', '8'];
-
 /// The board part of the initial position in the FEN format.
 const kInitialBoardFEN = 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR';
 

lib/src/debug.dart

@@ -2,7 +2,6 @@ import './board.dart';
 import './models.dart';
 import './position.dart';
 import './square_set.dart';
-import './utils.dart';
 
 /// Takes a string and returns a SquareSet. Useful for debugging/testing purposes.
 ///
@@ -34,7 +33,7 @@ SquareSet makeSquareSet(String rep) {
     for (int x = 0; x < 8; x++) {
       final repSq = table[y][x];
       if (repSq == '1') {
-        ret = ret.withSquare(x + y * 8);
+        ret = ret.withSquare(Square(x + y * 8));
       }
     }
   }
@@ -46,7 +45,7 @@ String humanReadableSquareSet(SquareSet sq) {
   final buffer = StringBuffer();
   for (int y = 7; y >= 0; y--) {
     for (int x = 0; x < 8; x++) {
-      final square = x + y * 8;
+      final square = Square(x + y * 8);
       buffer.write(sq.has(square) ? '1' : '.');
       buffer.write(x < 7 ? ' ' : '\n');
     }
@@ -59,7 +58,7 @@ String humanReadableBoard(Board board) {
   final buffer = StringBuffer();
   for (int y = 7; y >= 0; y--) {
     for (int x = 0; x < 8; x++) {
-      final square = x + y * 8;
+      final square = Square(x + y * 8);
       final p = board.pieceAt(square);
       final col = p != null ? p.fenChar : '.';
       buffer.write(col);
@@ -100,7 +99,7 @@ int perft(Position pos, int depth, {bool shouldLog = false}) {
     for (final entry in pos.legalMoves.entries) {
       final from = entry.key;
       final dests = entry.value;
-      final promotions = squareRank(from) == (pos.turn == Side.white ? 6 : 1) &&
+      final promotions = from.rank == (pos.turn == Side.white ? 6 : 1) &&
               pos.board.pawns.has(from)
           ? promotionRoles
           : [null];