From: Ken Bloom <kbloom@...>
Date: 2007-05-12T02:10:32+09:00
Subject: Re: Creating and adding new methods in runtime

On Fri, 11 May 2007 08:06:54 -0700, konryd wrote:

> Hello, I need to add in runtime several methods to my class. How can I
> accomplish this in ruby?
> More precisely: I need my class to overload arithmetic operators with
> fixnums in both ways (4+MyClass, MyClass+4). All the necessary info is
> stored in a hash, so I created a method to do all the stuff. It looks
> like do_operation(operator, other)
> But still I have to add every single operator overloader: class Fixnum
> 
>   def doo_operation(operator, other)
>   #...nevermind...
>   end
> 
>   def +(other)
>     do_operation(:+, other)
>   end
>   def -(other)
>     do_operation(:-, other)
>   end
> end
> 
> can I automate it somehow?

Just overrode MyClass#coerce, and the numeric operators on other classes 
will call coerce if they can't identify the class you're trying to 
perform arithmetic. Make sure there are +,-, etc... operators on MyClass, 
and make sure that they
(a) handle built-in numeric types
(b) handle MyClass+MyClass
(c) call coerce if they don't recognize the class on the right-hand side

There's more discussion of #coerce in PickAxe.

--Ken

-- 
Ken Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/