gistfile1.c

#define FPS 30

enum player_state {
  PLAYER_HALT,
  PLAYER_LEFT,
  PLAYER_RIGHT,
  PLAYER_DOWN,
  PLAYER_UP
};

struct player {
  double x, y, v;
  enum player_state state;
};


void animate_player(struct player *player) {
  double p0, p1, p2;

  double d = player->v / FPS;

  while (d) {
    switch(player->state) {

     case PLAYER_HALT:
      d = 0;
      break;

     case PLAYER_LEFT:
      p0 = player->x;
      p1 = p0 - d;
      p2 = ceil(p0 - 1);
      if (p1 < p2) {
        player->x = p2;
        d = p2 - p1;
      } else {
        player->x = p1;
        d = 0;
      }
      break;

     case PLAYER_RIGHT:
      p0 = player->x;
      p1 = p0 + d;
      p2 = floor(p0 + 1);
      if (p2 < p1) {
        player->x = p2;
        d = p1 - p2;
      } else {
        player->x = p1;
        d = 0;
      }
      break;

     case PLAYER_DOWN:
      p0 = player->y;
      p1 = p0 - d;
      p2 = ceil(p0 - 1);
      if (p1 < p2) {
        player->y = p2;
        d = p2 - p1;
      } else {
        player->y = p1;
        d = 0;
      }
      break;

     case PLAYER_UP:
      p0 = player->y;
      p1 = p0 + d;
      p2 = floor(p0 + 1);
      if (p2 < p1) {
        player->y = p2;
        d = p1 - p2;
      } else {
        player->y = p1;
        d = 0;
      }
      break;

    }
  }
}