Set includes and membership

require 'set'

primes = Set[2, 3, 5, 7]
primes.include? 2        # => true
primes.member? 1         # => false

1.	Create set with Set.new
2.	Create set with constant values
3.	Is it in a set
4.	Is it a subset
5.	Set length, size and empty?
6.	The intersection is the set of values that appear in both
7.	The union is the set of values that appear in either
8.	a-b: is the elements of a except for those also in b
9.	a^b is the set of values that appear in one set but not both: (a\|b)-(a&b)
10.	Add element to a set
11.	merge a range to a set
12.	Remove elements from a set
13.	Set subtraction
14.	Delete elements from a set with block
15.	Reject elements from a set
16.	Do an in-place intersection like this:
17.	Replace a set
18.	Clear a set
19.	Is it empty
20.	Each loop
21.	Map elements in a set
22.	Collect in place
23.	Convert set to array
24.	Inspect a set
25.	Compare two sets
26.	Classify set elements as even or odd
27.	Divide set
28.	Divide with block
29.	Flatten the subsets
30.	Add new method to set
31.	Partitioning or Classifying a Set
32.	Divide a set by value
33.	Divide a set by even and odd value
34.	Divide a set by its element's class
35.	Divide a set by absolute value
36.	Divide set into three sub sets
37.	Classify a set into three
38.	Convert a hash to set and divide
39.	Add set operation to Array
40.	Sort with block

Set includes and membership : Set « Collections « Ruby