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Question

I've pored over the chess programming wiki on bit-boards, but i'm still struggling with how i'm supposed to actually create them. From what I've gathered they're supposed to be a uint64_t right? Sometimes I see them represented as long hex looking numbers like in stockfish, and other times I see them represented as a 64 digit binary number.

How do I take, for example, an array of chessboard positions and convert those into bit-boards for each piece and then two for color?

Answer

Since things like unsigned long long are not guaranteed to have any particular number of bits, making use of cstdint a good idea here, like so:

#include <cstdint>
uint64_t board;

However, using std::bitset is likely to generate more readable code with less effort:

#include <bitset>
#include <cassert>
class BitBoard {
 private:
  std::bitset<64> board;
 public:
  auto operator()(int x, int y){
    assert(0<=x && x<=7);
    assert(0<=y && y<=7);
    return board[8*y+x];
  }
  void setAll(bool val){
    if(val)
      board.set();   //All bits on
    else
      board.reset(); //All bits off
  }
};
int main(){
  BitBoard board;
}

I am not sure off-handedly which one would be more performant. Others have posted thoughts about performance here.