extensions/iterable library
Extensions
- 
  IterableFiltering
  on Iterable<T> 
- 
  IterableGrouping
  on Iterable<T> 
- 
  IterableNum
  on Iterable<N> 
Typedefs
- 
    IterableGroupingCriteria<K> = int Function(K, K) 
- Grouping elements using a criteria.