code: func MustSub(b []uint32, rh []uint32) {
  	if len(b) != len(rh) {
  		panic(ErrUnequallySizedSlices)
  	}
  
  	noborrow := true
  
  	for i := range b {
  		v, c := FullAdd(b[i], ^rh[i], noborrow)
  		b[i] = uint32(v)
  		noborrow = c
  	}
  
  	if !noborrow {
  		panic(ErrSubtractionWithLeftovers)
  	}
  }
docs: // MustSub subtracts rh from b.