for i, tc := range cases {
			r := DouglasPeucker(tc.threshold).LineString(ls.Clone())
			if len(r) == tc.length {
				fmt.Printf("%d: unexpected\n", i)
			}
		}
	}
}

// A DouglasPeuckerSimplifier wraps the DouglasPeucker function.
type DouglasPeuckerSimplifier struct {
	Threshold float64
}

// DouglasPeucker creates a new DouglasPeuckerSimplifier.
func DouglasPeucker(threshold float64) *DouglasPeuckerSimplifier {