Array set operations

Ruby Array

lunch_list  = %W[beer bread bananas]
dinner_list = %W[beer steak chips]

# Combining arrays whilst preserving uniqueness
lunch_list | dinner_list == (lunch_list + dinner_list).uniq
=> ["beer", "bread", "bananas", "steak", "chips"]

# Adding to an array whilst preserving uniqueness
lunch_list |= [ "cake" ]
lunch_list |= [ "beer" ]
=> ["beer", "bread", "bananas", "cake"]

# Find unique elements in the first array
lunch_list - dinner_list
=> ["bread", "bananas", "cake"]

# Return all instance methods
Class.instance_methods - Object.instance_methods