From: Brian Candler <b.candler@...>
Date: 2009-01-05T18:58:12+09:00
Subject: Re: VERY simple question about "?"

Tom Cloyd wrote:
> * Operators - has the same problem as Thomas' book: precedence is shown,
> but basic operator function appears to be assumed to be known. I'm
> sorry, but I wasn't born with that knowledge. Look at this line: <=> ==
> === != =~ !~

There aren't really any operators in Ruby. Ruby simply maps all these to 
method calls (*), so to find out what the operator *means* you have to 
look at the class documentation for that method.

e.g.
  str1 = "foo"
  str2 = "bar"
  p str1 <=> str2

Here you need to look at the documentation for String#<=> to see what it 
means. Yes, "<=>" is a legitimate method name :-) You can also call it 
like this:

  str1.<=>(str2)

The only real purpose of the operator precedence table is to show how 
expressions containing multiple operators are resolved. e.g.

   1 + 2 * 3

#  same as:
#  1 + (2 * 3)

#  same as:
#  1.+(2.*(3))

Note that even the methods '+' and '*' do not necessarily have anything 
to do with addition or multiplication. It's entirely dependent on the 
target object how it implements these methods. For example:

   "123" * 3    # => "123123123"

HTH,

Brian.

(*) The exceptions in ruby 1.8 are != and !~, which invoke the methods 
== and =~ but then negate the result
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