C中的位板国际象棋编程

Question

我在C中的这段代码有问题.

#include <stdio.h>
#include <stdint.h>

typedef uint64_t bboard;

// Accessing a square of the bitboard
int
get (bboard b, int square)
{
  return (b & (1ULL << square));
}

void
print_board (bboard b)
{
  int i, j, square;
  for (i = 7; i >= 0; i--) // rank => top to bottom
    {
      for (j = 0; j < 8; j++) // file => left to right
        printf ("%d ", get (b, j+8*i) ? 1 : 0);
      printf ("\n");
    }
}

int
main ()
{
  bboard b = 0xffffffffffffffff;
  print_board (b);
}

// result that I have
0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 
1 1 1 1 1 1 1 1 
1 1 1 1 1 1 1 1 
1 1 1 1 1 1 1 1 
1 1 1 1 1 1 1 1 

好的,为什么位板没有设置为1位？

如有任何问题,请添加评论.泰:D

Answer 1

get返回一个int,但是(b & (1ULL << square))是uint64_t.当(b & (1ULL << square))大于时INT_MAX,结果是不确定的; 在这种情况下,它会截断并返回0.

如果get返回a bboard,则按预期工作(在此验证:http://codepad.org/zEZiJKeR).