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unsigned char *mvsQ[] = { &mvsNW[0][0], &mvsNE[0][0], &mvsSW[0][0], &mvsSE[0][0],
                          &mvsNN[0][0], &mvsEE[0][0], &mvsSS[0][0], &mvsSW[0][0] };

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void WSBBG(threadS *t, u08 id, u08 fs, u08 *inv, u64 *bb) {
  u08 i;
  u64 ray;

  do {
    i = FirstBit32(*inv);
    *inv ^= (1 << i);
    switch (i) {
    ...
   case NN:
      ray = (rayNN[fs] & belowInc[FirstBit64(rayNN[fs] & t->aPieces)] & ~t->wPieces);
      *bb &= andNN[fs];
       *bb |= ray; mvsNN[fs][0] = (u08)__popcnt64(ray);
      break;
  ...
      mvs = mvsQ[i];
    while (ray) {
      n++;
      ts = FirstBit64(ray);
      ray ^= one << ts;
      *(mvs + (((fs << 3) + n))) = ts; // I want to do something like,  mvs[fs][n] = ts;
    }
     *(mvs + (fs << 3)) = n;
    t->inv[t->brd[fs]][t->top[t->brd[fs]]] = 0;
  } while (*inv);
}
         

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*(mvs + (((fs << 3) + n))) = ts; // I want to do something like,  mvs[fs][n] = ts;

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TYPE_T mvs[8][8];
mvs[fs][n] = ts;
...
mvs[fs][0] = n; /*use a proper constant/define for 0 to avoid the magic number 0 here!*/

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std::array<std::array<int, 3>, 2> my_matrix {{
    {{0, 1, 2}},
    {{3, 4, 5}}
 }};

my_matrix[1][2] = 42;

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void foo()
{
    int arr[10];
    // ...
    bar(arr); // this works; int array arr decays to an int pointer
    
    std::array<int, 10> arr2;
    // ...
    bar(arr2); // compile-time error
}

void bar(int *arr)
{
    // ...
}

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// These are vectors for the bishop. Ex: mvsNW[A1][0] is the number of squares. [A1][1-7] are the to squares.
u08 mvsNW[64][8];
u08 mvsNE[64][8];
u08 mvsSE[64][8];
u08 mvsSW[64][8];

// This is an array of pointers to the above arrays.
unsigned char *mvsB[] = { &mvsNW[0][0], &mvsNE[0][0], &mvsSW[0][0], &mvsSE[0][0] };

// In this code I declare unsigned char *ptr and in line 4 it is assigned each array address by a for loop
// Then It is used with pointer arithmetic. But, I thought it would be possible to use it as an array name as in ptr[fs][j]
void WBf(threadS *t, u08 id, u08 depth, moveS *m) {
  unsigned char *ptr = &t->inv[id][t->top[id]];  m->fs = t->sqr[id];
  if (*ptr) WSBBG(t, id, m->fs, ptr, &t->stk[id][t->top[id]]);
  for (u08 i = 0; i < 4; i++) { ptr = mvsB[i];
    for (u08 j = 1; j <= *(ptr + (m->fs << 3)); j++) {
      m->ts = *(ptr + ((m->fs << 3) + j));
      m->id = t->brd[m->ts];
      m->typ = (m->id) ? WBC : WBM;
      MakeMove(t, m);
      if (depth > 0) Perft(t, depth - 1);
      TakeBack(t, m);
    }
  }
}

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// These are vectors for the bishop. Ex: mvsNW[A1][0] is the number of squares. [A1][1-7] are the to squares.
// Note that we have to declare the dimensions in reverse order, since we're explicitly nesting the types
std::array<std::array<u08, 8>, 64> mvsNW;
std::array<std::array<u08, 8>, 64> mvsNE;
std::array<std::array<u08, 8>, 64> mvsSE;
std::array<std::array<u08, 8>, 64> mvsSW;

// This is an array of pointers to the above arrays.
// Note that this is storing the exact same pointer as befores, but now it's preserving type information.
// We could have mvsB itself be a std::array, but it's not necessary.
std::array<std::array<u08, 8>, 64> * mvsB[] = { &mvsNW, &mvsNE, &mvsSW, &mvsSE };

// In this code I declare unsigned char *ptr and in line 4 it is assigned each array address by a for loop
// Then It is used with pointer arithmetic. But, I thought it would be possible to use it as an array name as in ptr[fs][j]
void WBf(threadS *t, u08 id, u08 depth, moveS *m) {
  unsigned char *ptr = &t->inv[id][t->top[id]];  m->fs = t->sqr[id];
  if (*ptr) WSBBG(t, id, m->fs, ptr, &t->stk[id][t->top[id]]);
  for (u08 i = 0; i < 4; i++) { 
    // Why are we dereferencing, and then holding a reference to the underlying array object? Why not leave it as a pointer?
    // Because otherwise we'd need to explicitly deference like this:
    // (*mvs)[m->fs][j]
    // BTW, if we just dereferenced, but didn't hold a reference, semantically we're asking the compiler to copy the contents of the array onto the stack.
    auto & mvs = *mvsB[i];
    for (u08 j = 1; j <= mvs[m->fs][0]; j++) {
      m->ts = mvs[m->fs][j];
      m->id = t->brd[m->ts];
      m->typ = (m->id) ? WBC : WBM;
      MakeMove(t, m);
      if (depth > 0) Perft(t, depth - 1);
      TakeBack(t, m);
    }
  }
}