code: func (l *d) mvL(r *d, c int) {
  	copy(l.d[l.c:], r.d[:c])
  	copy(r.d[:], r.d[c:r.c])
  	// Zero out the de's here to prevent reading bad data
  	// and to avoid creating non-collectible (GC) references.
  	for i := 1; i < c; i++ {
  		r.d[r.c-i] = zde
  	}
  	l.c += c
  	r.c -= c
  }
docs: // -------------------------------------------------------------------------- d