default direc=direc;
default bit=bit;
default gate=gate;
default ready=ready;

nbr y;
int result;

int PointAtMe(nbr y) {
  rot if (y:==we: && y:direc=='>')
    return 1;
  return 0;
}

int RightBridge(nbr y; int b) {
  if (b=='=:direc' && (y:==ea: || y:==we:) || 
      b=='H:direc' && (y:==no: || y:==so:))
    return 1;
  return 0;
}

if (bit) {
  rot if (direc=='>' && (ea:ready || ea:bit=='.' && RightBridge(ea:, ea:direc))
		 || ea:direc=='>' && ea:bit=='.')
   bit='.';
} else if (ready) {
  if (gate=='&') {
    result=1;
    over each other y:
      if (PointAtMe(y:))
        result = result & (y:bit-'0');
  } else if (gate=='|') {
    result=0;
    over each other y:
      if (PointAtMe(y:))
        result = result | (y:bit-'0');
  } else if (gate=='^') {
    result=1;
    over each other y:
      if (PointAtMe(y:))
        result = result & (y:bit-'0');
    result = 1 - result;
  }
  bit=result+'0:bit';
  ready=0;
} else if (gate) {
  result=1;
  over each other y:
    if (PointAtMe(y:) && y:bit=='.')
      result=0;
  ready=result;
} else if (direc && bit=='.') {
  rot if (we:bit && direc=='>' && (we:direc<'=' || RightBridge(we:, we:direc)))
    bit=we:bit;
  else rot if (RightBridge(we:, direc) && we:direc=='>' && we:bit)
      bit=we:bit;
  else rot if (RightBridge(we:, direc)==0 && we:direc=='>' && we:bit) {
    if (direc=='=')
      direc='H';
    else if (direc=='H')
      direc='=';
  }
}