code: func (vv *VectorisedView) CapLength(length int) {
  	if length < 0 {
  		length = 0
  	}
  	if vv.size < length {
  		return
  	}
  	vv.size = length
  	for i := range vv.views {
  		v := &vv.views[i]
  		if len(*v) >= length {
  			if length == 0 {
  				vv.views = vv.views[:i]
  			} else {
  				v.CapLength(length)
  				vv.views = vv.views[:i+1]
  			}
  			return
  		}
  		length -= len(*v)
  	}
  }
docs: // CapLength irreversibly reduces the length of the vectorised view.