The following gist link contains extension code for the List class in Dart.
https://gist.github.com/stijn1989/04b33b146a3048c04d036a28d8fabca5
powerSet
This method returns a new list of unique combinations of the items in the list.
sum
This method returns the sum of the items in the list. To obtain the numeric value of the item, you have to provide a callback.