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.  ab: 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: (ab)(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 inplace 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   
41.  Set includes and membership   