+#
+# ~~~
+# var c = new Counter[String].from(["a", "a", "b", "b", "b", "c"])
+# assert c["a"] == 2
+# assert c["b"] == 3
+# assert c["c"] == 1
+# assert c["d"] == 0
+# ~~~
+#
+# The counter class can also be used to gather statistical informations.
+#
+# ~~~~
+# assert c.length == 3 # because 3 distinct values
+# assert c.max == "b" # because "b" has the most count (3)
+# assert c.avg == 2.0 # because it is the mean of the counts
+# ~~~~