dir.h

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/* Definitions for directions of the compass.
   Copyright (C) 1987-1989, 1991-1994, 1996, 2001 Stanley T. Shebs.

Xconq is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.  See the file COPYING.  */

#define NUMDIRS 6

/* Symbols naming the directions. */

#define NODIR -1
#define NORTHEAST 0
#define EAST  1
#define SOUTHEAST 2
#define SOUTHWEST 3
#define WEST  4
#define NORTHWEST 5

#define DIRNAMES { "NE", "E", "SE", "SW", "W", "NW" }

#define DIRX { 0, 1,  1,  0, -1, -1 }
#define DIRY { 1, 0, -1, -1,  0,  1 }

#define for_all_directions(dir) \
for ((dir) = 0; (dir) < NUMDIRS; ++(dir))

/* \brief Interate through directions from random start.
 *
 * Iteration, starting with a random direction, but going in a
 * consistent order once started.  Generate a random number between
 * 0 and 5, inclusive, the step throught the directions using a modulo 
 * count.
 * \see xrandom, NUMDIRS.
 * \param dir is the direction iteration variable.
 * \param tmp is the starting direction (generated by xrandom).
 */
#define for_all_directions_randomly(dir,tmp)  \
  for ((tmp) = 0, (dir) = xrandom(NUMDIRS); (tmp) < NUMDIRS; ++(tmp), (dir) = ((dir) + 1) % NUMDIRS)

#define left_dir(d) (((d) + 5) % NUMDIRS)

#define right_dir(d) (((d) + 1) % NUMDIRS)

#define opposite_dir(d) (((d) + 3) % NUMDIRS)

#define dir_subtract(d1, d2) (((d1) - (d2) + NUMDIRS) % NUMDIRS)

#define angle_with(d1, d2)  \
  min(((d1) - (d2) + NUMDIRS) % NUMDIRS, ((d2) - (d1) + NUMDIRS) % NUMDIRS)

#define random_dir() (xrandom(NUMDIRS))

extern char *dirnames[];

extern int dirx[];
/*1 \brief Y delta array. */
extern int diry[];

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