Remove redundancy from S-Chess FEN

Closes #83.

diff --git a/src/position.cpp b/src/position.cpp
index acce8a4..3a06a42 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -717,7 +717,11 @@ string Position::fen(bool sfen, bool showPromoted, int countStarted, std::string
 
   if (gating() && gates(WHITE) && (!seirawan_gating() || count_in_hand(WHITE, ALL_PIECES) > 0 || captures_to_hand()))
       for (File f = FILE_A; f <= max_file(); ++f)
-          if (gates(WHITE) & file_bb(f))
+          if (   (gates(WHITE) & file_bb(f))
+              // skip gating flags redundant with castling flags
+              && !(!chess960 && can_castle(WHITE_CASTLING) && f == file_of(castling_king_square(WHITE)))
+              && !(can_castle(WHITE_OO ) && f == file_of(castling_rook_square(WHITE_OO )))
+              && !(can_castle(WHITE_OOO) && f == file_of(castling_rook_square(WHITE_OOO))))
               ss << char('A' + f);
 
   // Disambiguation for chess960 "king" square
@@ -732,7 +736,11 @@ string Position::fen(bool sfen, bool showPromoted, int countStarted, std::string
 
   if (gating() && gates(BLACK) && (!seirawan_gating() || count_in_hand(BLACK, ALL_PIECES) > 0 || captures_to_hand()))
       for (File f = FILE_A; f <= max_file(); ++f)
-          if (gates(BLACK) & file_bb(f))
+          if (   (gates(BLACK) & file_bb(f))
+              // skip gating flags redundant with castling flags
+              && !(!chess960 && can_castle(BLACK_CASTLING) && f == file_of(castling_king_square(BLACK)))
+              && !(can_castle(BLACK_OO ) && f == file_of(castling_rook_square(BLACK_OO )))
+              && !(can_castle(BLACK_OOO) && f == file_of(castling_rook_square(BLACK_OOO))))
               ss << char('a' + f);
 
   if (!can_castle(ANY_CASTLING) && !(gating() && (gates(WHITE) | gates(BLACK))))

diff --git a/test.py b/test.py
index 1f9e1b4..4f3ffde 100644 (file)
--- a/test.py
+++ b/test.py
@@ -14,7 +14,7 @@ SITTUYIN = "8/8/4pppp/pppp4/4PPPP/PPPP4/8/8[KFRRSSNNkfrrssnn] w - - 0 1"
 MAKRUK = "rnsmksnr/8/pppppppp/8/8/PPPPPPPP/8/RNSKMSNR w - - 0 1"
 SHOGI = "lnsgkgsnl/1r5b1/ppppppppp/9/9/9/PPPPPPPPP/1B5R1/LNSGKGSNL[-] w - - 0 1"
 SHOGI_SFEN = "lnsgkgsnl/1r5b1/ppppppppp/9/9/9/PPPPPPPPP/1B5R1/LNSGKGSNL b - 1"
-SEIRAWAN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR[HEhe] w KQBCDFGkqbcdfg - 0 1"
+SEIRAWAN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR[EHeh] w KQBCDFGkqbcdfg - 0 1"
 GRAND = "r8r/1nbqkcabn1/pppppppppp/10/10/10/10/PPPPPPPPPP/1NBQKCABN1/R8R w - - 0 1"
 GRANDHOUSE = "r8r/1nbqkcabn1/pppppppppp/10/10/10/10/PPPPPPPPPP/1NBQKCABN1/R8R[] w - - 0 1"
 XIANGQI = "rnbakabnr/9/1c5c1/p1p1p1p1p/9/9/P1P1P1P1P/1C5C1/9/RNBAKABNR w - - 0 1"
@@ -330,6 +330,14 @@ class TestPyffish(unittest.TestCase):
         result = sf.get_fen("xiangqi", XIANGQI, [])
         self.assertEqual(result, XIANGQI)
 
+        result = sf.get_fen("seirawan", SEIRAWAN, [])
+        self.assertEqual(result, SEIRAWAN)
+
+        # test idempotence for S-Chess960 gating flags
+        fen1 = sf.get_fen("seirawan", SEIRAWAN, [], True)
+        fen2 = sf.get_fen("seirawan", fen1, [], True)
+        self.assertEqual(fen1, fen2)
+
         fen = "rnab1kbcnr/ppppPppppp/10/4q5/10/10/PPPPP1PPPP/RNABQKBCNR[p] b KQkq - 0 3"
         result = sf.get_fen("capahouse", CAPA, ["f2f4", "e7e5", "f4e5", "e8e5", "P@e7"])
         self.assertEqual(result, fen)

diff --git a/tests/js/test.js b/tests/js/test.js
index af31857..f53052a 100644 (file)
--- a/tests/js/test.js
+++ b/tests/js/test.js
@@ -741,7 +741,7 @@ describe('ffish.readGamePGN(pgn)', function () {
      let expectedFens = ["1r6/5kp1/RqQb1p1p/1p1PpP2/1Pp1B3/2P4P/6P1/5K2 b - - 14 45",
                          "3r2kr/2pb1Q2/4ppp1/3pN2p/1P1P4/3PbP2/P1P3PP/6NK[PPqrrbbnn] b - - 1 37",
                          "r1bqkbnr/pppp1ppp/2n5/1B2p3/4P3/5N2/PPPP1PPP/RNBQK2R b KQkq - 3 3",
-                         "r1bQkb1r/ppp1pppp/2P5/2n2q2/8/2N2N2/PPP2PPP/R1BEKB1R[Hh] b KQACEFHkqacefh - 0 8",
+                         "r1bQkb1r/ppp1pppp/2P5/2n2q2/8/2N2N2/PPP2PPP/R1BEKB1R[Hh] b KQCFkqcf - 0 8",
                          "5rk1/4p3/2p3rR/2p1P3/2Pp1B2/1P1P2P1/2N1n3/6K1 w - - 1 44"]
 
      for (let idx = 0; idx < pgnFiles.length; ++idx) {