mapfn(i, s.GetValue(i))// Maybe you mean -> output[i] =mapfn(i, s.GetValue(i))

[zxysilent]

func (s Seq) Map(mapfn func(i int, v float64) float64) Seq {
	output := make([]float64, s.Len())
	for i := 0; i < s.Len(); i++ {
		mapfn(i, s.GetValue(i))// Maybe you mean -> xxoutput[i] =mapfn(i, s.GetValue(i))
	}
	return Seq{Array(output)}
}