[Freeciv-Dev] Re: [PATCH] city_map_size fix and idea

[Trent Piepho <xyzzy@xxxxxxxxxxxxx>]

On Wed, 22 Aug 2001, Ross W. Wetmore wrote:
> +    tileno = INDEX_NSEW(
> +      (is_real_tile(abs_x0, abs_y0-1)
> +        && (tile_is_known(abs_x0, abs_y0-1)==TILE_UNKNOWN)),
> +      (is_real_tile(abs_x0, abs_y0+1)
> +        && (tile_is_known(abs_x0, abs_y0+1)==TILE_UNKNOWN)),
> +      (is_real_tile(abs_x0+1, abs_y0)
> +        && (tile_is_known(abs_x0+1, abs_y0)==TILE_UNKNOWN)),
> +      (is_real_tile(abs_x0-1, abs_y0)
> +        && (tile_is_known(abs_x0-1, abs_y0)==TILE_UNKNOWN)));

It looks like your change doesn't normalize the coordinates.  Isn't there some
sort of cardinal map iterator function that could be used here? 

Something sort of like this...

  int x,y,dir, n=0,s=0,e=0,w=0;

  /* Find which of the cardinal directions are unknown */
  adj_card_dir_iterate(abs_x0, abs_y0, x, y, dir) {
    if(tile_is_known(x,y)==TILE_UNKNOWN) {
      switch(dir) {
        case DIR8_NORTH:  n=1; break;
        case DIR8_SOUTH:  s=1; break;
        case DIR8_EAST:   e=1; break;
        case DIR8_WEST:   w=1; break;
      }
    }
  } adj_card_dir_iterate_end;
  tileno = INDEX_NSEW(n,s,e,w);

It make look a little more complex, but I think once you make the previous way
normalize coordinates, it will be simpler.  Also keep in mind that the iterate
macro is smart, and if the center tile isn't on the map boundary, it avoids
the check for is_real_tile() and doesn't normalize the coordinates.

I don't know if adj_card_dir_iterate exists, but it should!  If it doesn't..

adj_dir_iterate(...) {
  if(!IS_CARDINAL(dir)) continue;

Does the same thing, but is less efficient, since the iterator macro will
still generate and normalize the non-cardinal points we aren't interested in.
I'm sure you remember, that if the directions use the DIR_DX2 order that
a cardinal iterate can be done by incrementing dir by 2 each iteration.