Bitwise AND XOR on conditional statement

Question

I'm trying to understand this snippet

for (; game->boxes_left > 0; game->turns++)
      {
      if ( (game->turns & 1) ^ game->computer_first )
         game->human_move();
      else
         game->computer_move();
      }

as inf game->turns is an integer, and it has increasing value , and game->comp_first is a boolean, Will anyone please tell me how if ( (game->turns & 1) ^ game->computer_first ) return it's 1 (true) or 0 (false) ? because what I understand & is bitwise operator and when turns & 1 it will always return 0 , as turns is an increasing value, what is the function of (game->turns & 1) in this if statement? is there any way to write this snippet in java. Thanks in advance

Answer 1

As game->turns goes through consecutive values, its last bits switches between 0 and 1 on each iteration. As the result, game->turns & 1 goes between 0 and 1 as well. XOR-ing the result with a bool gives you the same value if bool is false, and an inverted value if bool is true.

game->turns   Last bit   XOR 0    XOR 1
-----------   --------   -----    -----
          0          0       0        1
          1          1       1        0
          2          0       0        1
          3          1       1        0
          4          0       0        1
          5          1       1        0

Note how the sequence goes 0-1-0-1-0-1 when game->computer_first is false, and 1-0-1-0-1-0 when game->computer_first is true.

To convert this snippet to Java, compare the result of game.turns & 1 with ):

if (((game.turns & 1) != 0) ^ game->computer_first) ...