[Freeciv-Dev] Re: [PATCH] more small directional cleanups

[Trent Piepho <xyzzy@xxxxxxxxxxxxx>]

On Mon, 20 Aug 2001, Jason Dorje Short wrote:
> I added an assertion to make sure the loop terminates (if debugging;
> otherwise we assume it terminates).  Bailing out won't really do any
> good since it would leave the game in an unstable state.


Here are I think better ways to do it.  My rand_neighbor function will run in
a bounded time, and will aways find a neighbor if one exists.

void rand_neighbor(int x0, int y0, int *x, int *y)
{
  int n, choice;
  int dirs[8] = {DIR8_NORTH, DIR8_NORTHEAST, DIR8_EAST, DIR8_SOUTHEAST,
                 DIR8_SOUTH, DIR8_SOUTHWEST, DIR8_WEST, DIR8_NORTHWEST};
  
  for(n=8;n>0;n--) {            /* We get 8 chances to find a spot */
    choice = myrand(n);
    *x = x0 + DIR_DX[dirs[choice]];
    *y = y0 + DIR_DY[dirs[choice]];

    if(normalize_map_pos(x, y)) return;  /* Found a valid spot! */

    /* Choice was bad, so replace it with the last direction in the list.
     * On the next iteration, one fewer choices will remain. */
    dirs[choice] = dirs[n-1];
  }
  /* What the hell?  No valid neighbor tiles.  This is a 1x1 map?  */
  assert(0);
}


This is I think a little nicer way to do dir_get_name().

const char *dir_get_name(enum direction8 dir)
{
  /* a switch statement is used so the ordering can be changed easily */
  switch(dir) {
    case DIR8_NORTH:     return "N";
    case DIR8_NORTHEAST: return "NE";
    case DIR8_EAST:      return "E";
    case DIR8_SOUTHEAST: return "SE";
    case DIR8_SOUTH:     return "S";
    case DIR8_SOUTHWEST: return "SW";
    case DIR8_WEST:      return "W";
    default:
      assert(0);
      return "Bad Direction";
  }
}