occurrences method

Map<T, int> occurrences()

Returns a new Map with the number of occurrences of each element.

Implementation

Map<T, int> occurrences() {
  Map<T, int> map = {};

  for (T e in this) {
    if (map.containsKey(e)) {
      map[e] = map[e]! + 1;
    } else {
      map[e] = 1;
    }
  }
  return map;
}