anchor.diff:  
   import FIFO::*;
   import Leds::*;
  +import Vector::*;
   
   interface EchoIndication;
       method Action heard(Bit#(32) v);
  
positive.code:       endmethod
        
        method Action setLeds(Bit#(8) v);
  	 ledsReg <= v;
        endmethod
     endinterface
     interface LEDS leds;
        method Bit#(8) leds();
           return ledsReg;
        endmethod
     endinterface
  
negative.code: 
      FIFO#(Bit#(32)) delay <- mkSizedFIFO(8);
      FIFO#(EchoPair) delay2 <- mkSizedFIFO(8);
      Reg#(Bit#(LedsWidth)) ledsReg <- mkReg(0);
  
      rule heard;
          delay.deq;
  