From: Brian Candler <b.candler@...>
Date: 2010-07-11T01:08:55+09:00
Subject: Re: if statements and case statements questions

Kenneth     wrote:
> Ruby switches expand to the === operator, for example:
> 
> case string
> when "" then puts "Empty"
> when /^a/ then puts "Starts with a"
> end
> 
> is equivalent to:
> 
> if string === ""
>   puts "Empty"
> elsif string === /^a/
>   puts "Contains a"
> end

Actually the arguments are the other way round:

if "" === string
  puts "Empty"
elsif /^a/ === string
  puts "Starts with a"
end

Another example:

case arg
when String; puts "it's a string"
when Numeric; puts "it's a number"
end

The first expands to String === arg, which is functionally equivalent to 
arg.is_a?(String)
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