panic(fmt.Sprintf("got %s, want %s", got, want))
	}

	got = _DoubleElems(arg)
	if !reflect.DeepEqual(got, want) {
		panic(fmt.Sprintf("got %s, want %s", got, want))
	}

	farg := MyFloatSlice{1.2, 2.0, 3.5}
	fwant := MyFloatSlice{2.4, 4.0, 7.0}
	fgot := _DoubleElems(farg)
	if !reflect.DeepEqual(fgot, fwant) {
		panic(fmt.Sprintf("got %s, want %s", fgot, fwant))
	}

	fgot = _DoubleElems2(farg)