Ruby: Counting occurrences of an item in an array / enumerable

Enumerable#count Show archive.org snapshot can do three things.

• With no argument provided, it returns the number of items.
• With an argument, it returns the number of items matching the given value.
• With a block, it counts the number of elements yielding a truthy value.

Copyary = [1, 2, 4, 2]
ary.count #=> 4
ary.count(2) #=> 2
ary.count { |x| x % 2 == 0 } #=> 3