Hash.new « Hash « Ruby

1.	Creating Hashes
2.	You can test to see if a hash is empty with empty?
3.	Test how big it is with length or size
4.	use new to create a hash with a default value which is otherwise just nil
5.	access any key in a hash that has a default value
6.	Hash with =>
7.	Hash.new with block logic
8.	This lazily initialized hash maps integers to their factorials

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