src/move.cpp

   1 /*
   2   Glaurung, a UCI chess playing engine.
   3   Copyright (C) 2004-2008 Tord Romstad
   4
   5   Glaurung is free software: you can redistribute it and/or modify
   6   it under the terms of the GNU General Public License as published by
   7   the Free Software Foundation, either version 3 of the License, or
   8   (at your option) any later version.
   9
  10   Glaurung is distributed in the hope that it will be useful,
  11   but WITHOUT ANY WARRANTY; without even the implied warranty of
  12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13   GNU General Public License for more details.
  14
  15   You should have received a copy of the GNU General Public License
  16   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19
  20 ////
  21 //// Includes
  22 ////
  23
  24 #include <cassert>
  25
  26 #include "move.h"
  27 #include "piece.h"
  28 #include "position.h"
  29 #include "ucioption.h"
  30
  31
  32 ////
  33 //// Functions
  34 ////
  35
  36 /// move_from_string() takes a position and a string as input, and attempts to
  37 /// convert the string to a move, using simple coordinate notation (g1f3,
  38 /// a7a8q, etc.).  In order to correctly parse en passant captures and castling
  39 /// moves, we need the position.  This function is not robust, and expects that
  40 /// the input move is legal and correctly formatted.
  41
  42 Move move_from_string(const Position &pos, const std::string &str) {
  43   Square from, to;
  44   Piece piece;
  45   Color us = pos.side_to_move();
  46
  47   if(str.length() < 4) return MOVE_NONE;
  48
  49   // Read the from and to squares:
  50   from = square_from_string(str.substr(0, 2));
  51   to = square_from_string(str.substr(2, 4));
  52
  53   // Find the moving piece:
  54   piece = pos.piece_on(from);
  55
  56   // If the string has more than 4 characters, try to interpret the 5th
  57   // character as a promotion:
  58   if(type_of_piece(piece) == PAWN && str.length() >= 5) {
  59     switch(str[4]) {
  60     case 'n': case 'N':
  61       return make_promotion_move(from, to, KNIGHT);
  62     case 'b': case 'B':
  63       return make_promotion_move(from, to, BISHOP);
  64     case 'r': case 'R':
  65       return make_promotion_move(from, to, ROOK);
  66     case 'q': case 'Q':
  67       return make_promotion_move(from, to, QUEEN);
  68     }
  69   }
  70
  71   if(piece == king_of_color(us)) {
  72     // Is this a castling move?  A king move is assumed to be a castling
  73     // move if the destination square is occupied by a friendly rook, or
  74     // if the distance between the source and destination squares is more
  75     // than 1.
  76     if(pos.piece_on(to) == rook_of_color(us))
  77       return make_castle_move(from, to);
  78     else if(square_distance(from, to) > 1) {
  79       // This is a castling move, but we have to translate it to the
  80       // internal "king captures rook" representation.
  81       SquareDelta delta = (to > from)? DELTA_E : DELTA_W;
  82       Square s;
  83       for(s = from + delta;
  84           pawn_rank(us, s) == RANK_1 && pos.piece_on(s) != rook_of_color(us);
  85           s += delta);
  86       if(pawn_rank(us, s) == RANK_1 && pos.piece_on(s) == rook_of_color(us))
  87         return make_castle_move(from, s);
  88     }
  89   }
  90   else if(piece == pawn_of_color(us)) {
  91     // En passant move?  We assume that a pawn move is an en passant move
  92     // without further testing if the destination square is epSquare.
  93     if(to == pos.ep_square())
  94       return make_ep_move(from, to);
  95   }
  96
  97   return make_move(from, to);
  98 }
  99
 100
 101 /// move_to_string() converts a move to a string in coordinate notation
 102 /// (g1f3, a7a8q, etc.).  The only special case is castling moves, where we
 103 /// print in the e1g1 notation in normal chess mode, and in e1h1 notation in
 104 /// Chess960 mode.
 105
 106 const std::string move_to_string(Move move) {
 107   std::string str;
 108
 109   if(move == MOVE_NONE)
 110     str = "(none)";
 111   else if(move == MOVE_NULL)
 112     str = "0000";
 113   else {
 114     if(!Chess960) {
 115       if(move_from(move) == SQ_E1 && move_is_short_castle(move)) {
 116         str = "e1g1"; return str;
 117       }
 118       else if(move_from(move) == SQ_E1 && move_is_long_castle(move)) {
 119         str = "e1c1"; return str;
 120       }
 121       if(move_from(move) == SQ_E8 && move_is_short_castle(move)) {
 122         str = "e8g8"; return str;
 123       }
 124       else if(move_from(move) == SQ_E8 && move_is_long_castle(move)) {
 125         str = "e8c8"; return str;
 126       }
 127     }
 128     str = square_to_string(move_from(move)) + square_to_string(move_to(move));
 129     if(move_promotion(move))
 130       str += piece_type_to_char(move_promotion(move), false);
 131   }
 132   return str;
 133 }
 134
 135
 136 /// Overload the << operator, to make it easier to print moves.
 137
 138 std::ostream &operator << (std::ostream &os, Move m) {
 139   return os << move_to_string(m);
 140 }
 141
 142
 143 /// move_is_ok(), for debugging.
 144
 145 bool move_is_ok(Move m) {
 146   return square_is_ok(move_from(m)) && square_is_ok(move_to(m));
 147 }