IntSegmentedTuple constructor
Implementation
IntSegmentedTuple([int? log_blksize_, int? base_size_]) {
if (log_blksize_ != null) log_blksize = log_blksize_;
if (base_size_ != null) base_size = (base_size_ <= 0 ? 4 : base_size_);
base = List.filled(base_size, []);
}