From: Gareth Adams <gareth.adams@...>
Date: 2006-11-25T18:40:14+09:00
Subject: Re: coding practise

> sempsteen <sempsteen <at> gmail.com> writes:

Hi,

I don't know too much about amicable numbers, but I can answer the first one...

> 1-) What does "Hash#has_key?" actually do?
> Why do we need such a method in spite of using the result of "Hash#[]"
> method which will return nil for a non-present key.

hsh = { :a => 5, :b => nil }

hsh.has_key? :a # => true
hsh[:a] # => 5
hsh.has_key? :b # => true
hsh[:b] # => nil
hsh.has_key? :c # => false
hsh[:c] # => false

Note that when the value of the hash item is nil or false, you'll get a
difference between #as_key? and #[]