anchor.diff:  	 end
   	 x <= newx;
   	 y <= newy;
  +	 isLastReg <= (newx+xstep >= xlimit && newy+ystep >= ylimit);
  +	 isFirstReg <= False;
         endmethod
         method Bool notEmpty();
   	 return guard;
  
positive.code:       ystep <= cfg.ystep;
        xlimit <= cfg.xlimit;
        ylimit <= cfg.ylimit;
     endmethod
     method Action display();
        $display("XYRangePipe x=%d xlimit=%d y=%d ylimit=%d xstep=%d ystep=%d", x, xlimit, xstep, y, ylimit, ystep);
     endmethod
  
negative.code:    Reg#(a) xlimit <- mkReg(0);
     Reg#(a) ylimit <- mkReg(0);
     
     Reg#(Bool) isFirstReg <- mkReg(False);
     Reg#(Bool) isLastReg <- mkReg(False);
  
     let guard = x < xlimit && y < ylimit;
     
     interface PipeOut pipe;
  