takeEveryNth method
Takes every n-th element (1-based: first, then 1+n, 1+2n, ...). n must be positive.
Implementation
@useResult
Iterable<T> takeEveryNth(int n) {
if (n < 1) throw ArgumentError(_kErrNPositive, _kParamN);
return zipWithIndex().where(((int, T) p) => p.$1 % n == 0).map(((int, T) p) => p.$2);
}