ABS
d1 = ABS(x_2 - x_1);
d2 = ABS(y_2 - y_1);
if (ABS(p1->altitude - p2->altitude) <= dist &&
ABS(p1->xpos - p2->xpos) <= dist && ABS(p1->ypos - p2->ypos) <= dist)
dx = x2-x1; ax = ABS(dx)<<1; sx = SGN(dx); x = x1;
dy = y2-y1; ay = ABS(dy)<<1; sy = SGN(dy); y = y1;
&temp[i])) || ABS(temp[i]) == 128 || temp[i] == 0)
&data)) || ABS(data) == 128 || data == 0) {
use0 = (ABS(speed - s0) < ABS(speed - s1))? 1 : 0;