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Ruby Programming
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Boolean Expressions

Ruby has a simple definition of truth. Any value that is not nil or the constant false is true. You'll find that the library routines use this fact consistently. For example, IO#gets , which returns the next line from a file, returns nil at end of file, enabling you to write loops such as:

while line = gets
  # process line
end

However, there's a trap here for C, C++, and Perl programmers. The number zero is not interpreted as a false value. Neither is a zero-length string. This can be a tough habit to break.
Ruby Programming
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