From: ts <decoux@...>
Date: 2004-05-02T20:43:20+09:00
Subject: Re: Commutativity of '*'

>>>>> "S" == =?ISO-8859-1?Q?Stephan K=E4mper?= <ISO-8859-1> writes:

S> # But this won't. Instead I get:
S> # .../lm.rb:25:in `*': Foo can't be coerced into Float (TypeError)

 Well, ruby is saying that it can coerce, learn it how to do it

 One way to do it

svg% cat b.rb
#!/usr/bin/ruby
def some_operation_using( lft, rgt )
   "#{lft} times #{rgt}"
end

class Foo

   def *(other)
      # do something
      res = some_operation_using( other, self )
      res
   end

   def coerce(other)
      case other
      when Numeric
         [self, other]
      else
         raise TypeError
      end
   end

   def to_s
      "a Foo thingy."
   end

end

f = Foo.new
puts f * 42.0
puts 42.0 * f
svg% 

svg% b.rb
42.0 times a Foo thingy.
42.0 times a Foo thingy.
svg% 



Guy Decoux