funcsPZ.go
func SubstrF(index, n int) func(string) string {
	return func(s string) string {
		return Substr(s, index, n)
	}
}
func SubstrF(index, n int) func(string) string {
	return func(s string) string {
		return Substr(s, index, n)
	}
}
// SubstrF is the filter form of Substr.