bits.py

   1 # bits.py
   2 # 1 Mar 2007
   3 # Make bitfields for piece moves.
   4
   5 """
   6     This file is part of Arrocco, which is Copyright 2007 Thomas Plick
   7     (tomplick 'at' gmail.com).
   8
   9     Arrocco is free software; you can redistribute it and/or modify
  10     it under the terms of the GNU General Public License as published by
  11     the Free Software Foundation; either version 3 of the License, or
  12     (at your option) any later version.
  13
  14     Arrocco is distributed in the hope that it will be useful,
  15     but WITHOUT ANY WARRANTY; without even the implied warranty of
  16     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17     GNU General Public License for more details.
  18
  19     You should have received a copy of the GNU General Public License
  20     along with this program.  If not, see <http://www.gnu.org/licenses/>.
  21 """
  22
  23 def bitsForKing(sq):
  24     r1, c1 = divmod(sq, 8)
  25     return [i for i in range(64) for (r2, c2) in [divmod(i, 8)]
  26                 if max(abs(r1-r2), abs(c1-c2)) == 1]
  27
  28 def bitsForKnight(sq):
  29     r1, c1 = divmod(sq, 8)
  30     return [i for i in range(64) for (r2, c2) in [divmod(i, 8)]
  31                 if abs(r1-r2) * abs(c1-c2) == 2]
  32
  33 def bitfieldForBits(bits):
  34     return sum(2**i for i in bits if i >= 0 and i < 64)
  35
  36 def bitsForPawnMove(sq, direc, firstRow):
  37     L = [sq + direc * 8]
  38     if sq // 8 == firstRow:
  39         L.insert(0, sq + direc * 16)
  40     return L
  41
  42 def bitsForPawnCapture(sq, direc):
  43     r, c = divmod(sq, 8)
  44     L = []
  45     if c > 0:  L.append((r+direc) * 8 + (c - 1))
  46     if c < 7:  L.append((r+direc) * 8 + (c + 1))
  47     return L
  48
  49 def bitsForHorizontalRookDests(sq, occupancy):
  50     r, c1 = divmod(sq, 8)
  51     occupiedColumns = [c for c in range(8) if occupancy & (1 << c)]
  52     for c2 in range(c1 + 1, 8):
  53         yield 8 * r + c2
  54         if c2 in occupiedColumns:
  55             break
  56     for c2 in range(c1 - 1, -1, -1):
  57         yield 8 * r + c2
  58         if c2 in occupiedColumns:
  59             break
  60
  61 def bitsForVerticalRookDests(sq, occupancy):
  62     r1, c = divmod(sq, 8)
  63     occupiedRows = [r for r in range(8) if occupancy & (1 << r)]
  64     for r2 in range(r1 + 1, 8):
  65         yield 8 * r2 + c
  66         if r2 in occupiedRows:
  67             break
  68     for r2 in range(r1 - 1, -1, -1):
  69         yield 8 * r2 + c
  70         if r2 in occupiedRows:
  71             break