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class NilClass
Parent: Object
Version: 1.6

Index:

& ^ | nil? to_a to_i to_s

The class of the singleton object nil.

instance methods
& nil & anObject -> false
And-Returns false. As anObject is an argument to a method call, it is always evaluated; there is no short-circuit evaluation in this case. 

nil && puts("logical and")
nil &  puts("and")

produces: 

and

^ nil ^ anObject -> true or false
Exclusive Or-Returns false if anObject is nil or false, true otherwise.
| nil | anObject -> true or false
Or-Returns false if anObject is nil or false, true otherwise.
nil? nil.nil? -> true
Always returns true.
to_a nil.to_a -> []
Always returns an empty array.
to_i nil.to_i -> 0
Always returns zero.
to_s nil.to_s -> ""
Always returns the empty string.

Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2000 Addison Wesley Longman, Inc. Released under the terms of the Open Publication License V1.0.
This reference is available for download.