+ end
+
+ # Packs elements into separate arrays based on their occurences
+ #
+ # ~~~nit
+ # var x = "aaaabbbeeecccddhhgjt"
+ # var c = new Counter[Char]
+ # for i in x do c.inc i
+ # var ret = c.pack
+ # assert ret.join(", ") == """[t,g,j], [d,h], [c,b,e], [a]"""
+ # ~~~
+ fun pack: Array[Array[E]] do
+ var ret = new Array[Array[E]]
+ var base = self.sort
+ if base.is_empty then return ret
+ var curr = new Array[E]
+ curr.push base.first
+ var curr_score = self[base.first]
+ base.shift
+ for i in base do
+ if self[i] == curr_score then
+ curr.push i
+ continue
+ end
+ curr_score = self[i]
+ ret.push curr
+ curr = new Array[E]
+ curr.push i
+ end
+ if not curr.is_empty then ret.push curr
+ return ret
+ end
+end
+
+redef class Collection[E]
+ # Create and fill up a counter with the elements of `self.
+ #
+ # ~~~
+ # var cpt = "abaa".chars.to_counter
+ # assert cpt['a'] == 3
+ # assert cpt['b'] == 1
+ # assert cpt.length == 2
+ # assert cpt.sum == 4
+ # ~~~
+ fun to_counter: Counter[E]
+ do
+ var res = new Counter[E]
+ res.inc_all(self)
+ return res