part of coreVector's first refactor attempt

int _kit_coreVectorSetUnitAxis(kit_coreVector** Vector_p, char axis, lens_t newLen){
  _IF_SDLERR(!newLen,;,"!newLen")
  kit_coreVector* Vector=*Vector_p;
  int isLowerCase = IS_LOWER(axis); //if axis was uppercase, keep oldSize set to 0
  SET_TO_LOWER(axis); //assuming ascii-like encoding

  _asize_t oldSize = 0;
  _asize_t newSize = Vector->unit*newLen;

  if(axis=='x'){ //implies vector is 1D
    _IF_SDLERR((Vector->_dims&3)!=1,;,"x && !1D")

    oldSize =sizeof(kit_coreVector);
    newSize+=sizeof(kit_coreVector);
    if(isLowerCase) oldSize += Vector->unit*Vector->x;
    if(oldSize == newSize) return 0;

    _IF_GOTO_ERROR(_kit_coreVectorRealloc(Vector_p, 'x', oldSize,newSize),;)

    Vector->x=newLen;
    *Vector_p=Vector;

  } else if(axis=='y'){ //implies vector is 2D
    _IF_SDLERR((Vector->_dims&3)!=2,;,"y && !2D")

    if(isLowerCase) oldSize = Vector->unit*Vector->y;

    void** p2d=Vector->p2d;
    lens_t x_len=Vector->x;
    for(lens_t xi=0; xi<x_len; ++xi)
      _IF_GOTO_ERROR(_kit_coreVectorRealloc(&p2d[xi], 'y', oldSize*(p2d[xi]!=NULL),newSize),;)

    if(x_len) Vector->y=newLen;

  } else if(axis=='z'){ //implies vector is 3D
    _IF_SDLERR((Vector->_dims&3)!=3,;,"z && !3D")

    if(isLowerCase) oldSize = Vector->unit*Vector->z;

    void*** p3d=Vector->p3d;
    lens_t x_len=Vector->x;
    lens_t y_len=Vector->y;
    for(lens_t xi=0; xi<x_len; ++xi){
      void** p2d=p3d[xi];
      for(lens_t yi=0; yi<y_len; ++yi)
        _IF_GOTO_ERROR(_kit_coreVectorRealloc(&p2d[yi], 'z', oldSize*(p2d[yi]!=NULL),newSize),;)
    }

    if(x_len && y_len) Vector->z=newLen;

  } else _IS_SDLERR(;,"axis=%c",axis)

  /*!err*/ return  0; // 0 on success
  _error_: return -1; //-1 on failure
}

//by "Add" i mean setting to a new length GREATER than the previous length
int _kit_coreVectorAddPointerAxis(kit_coreVector** Vector_p, char axis, lens_t newLen){
  _IF_SDLERR(!newLen,;,"!newLen")
  kit_coreVector* Vector=*Vector_p;
  int isLowerCase = IS_LOWER(axis); //if axis was uppercase, keep oldSize set to 0
  SET_TO_LOWER(axis); //assuming ascii-like encoding

  _asize_t oldSize = 0;
  _asize_t newSize = sizeof(void*)*newLen;
  if(axis=='x'){
    //shift both forward by size of kit_coreVector struct
    newSize += oldSize=sizeof(kit_coreVector);
    if(isLowerCase) oldSize += sizeof(void*)*Vector->x;
  } else if(axis=='y') {
    //(= is the same as += if oldSize was 0)
    if(isLowerCase) oldSize  = sizeof(void*)*Vector->y;
  } else _IS_SDLERR(;,"axis=%c",axis)

  void** p2d=Vector->p2d;
  int dims=Vector->_dims&3;
  switch((dims<<8)|axis){
  case (0x200|'x'): //2D, x axis
    if(Vector->x == newLen) break;
    _IF_SDLERR(newLen<Vector->x,;,"newLen<x");

    //extend x
    _IF_GOTO_ERROR(_kit_coreVectorRealloc(Vector_p, 'x', oldSize,newSize),;)
    Vector->x=newLen; //update x length to new value

    //fill in new x indices with additional y units
    _IF_GOTO_ERROR(_kit_coreVectorSetUnitAxis(Vector_p, 'y', Vector->y),;)
    break;

  case (0x300|'x'): //3D, x axis
    if(Vector->x == newLen) break;
    _IF_SDLERR(newLen<Vector->x,;,"newLen<x");

    //extend x
    _IF_GOTO_ERROR(_kit_coreVectorRealloc(Vector_p, 'x', oldSize,newSize),;)
    lens_t x_old = Vector->x;
    lens_t x_new = Vector->x=newLen; //(also updates x length to new value)

    //put additional y pointers in new x indices
    _asize_t y_size = sizeof(void*)*Vector->y;
    p2d=Vector->p2d;
    for(lens_t xi=x_old; xi<x_new; ++xi)
      _IF_GOTO_ERROR(_kit_coreVectorRealloc(&p2d[xi], 'y', 0,y_size),;)

    //fill in new y indices with additional z units
    _IF_GOTO_ERROR(_kit_coreVectorSetUnitAxis(Vector_p, 'z', Vector->z),;)
    break;

  case (0x300|'y'):; //3D, y axis
    if(Vector->y == newLen) break;
    _IF_SDLERR(newLen<Vector->y,;,"newLen<y");

    //extend y
    lens_t x_len = Vector->x;
    p2d=Vector->p2d;
    for(lens_t xi=0; xi<x_len; ++xi)
      _IF_GOTO_ERROR(_kit_coreVectorRealloc(&p2d[xi], 'y', oldSize,newSize),;)
    Vector->y=newLen; //update y length to new value

    //fill in new y indices with additional z units
    _IF_GOTO_ERROR(_kit_coreVectorSetUnitAxis(Vector_p, 'z', Vector->z),;)
    break;

  default: _IS_SDLERR(;,"%uD && %c", dims, axis)
  }

  /*!err*/ return  0; // 0 on success
  _error_: return -1; //-1 on failure
}