From: Mathieu Bouchard <matju@...>
Date: 2002-01-24T00:24:18+09:00
Subject: Re: Newbie: simple data-type problem


On Wed, 23 Jan 2002, Dave Carmean wrote:
> What I though I'd try is to create a class which inherits from 
> Fixnum, and do range checking in the initializer.  Doesn't work. 
> Can't figure out how to initialize it, because Fixnum doesn't have 
> a new() method.

Classes are there to add functionality, not remove it. You want to
describe a subset of the Fixnum class in which all methods are the same. I
have worked on a concept of "type" separate from "class" to deal with this
kind of problem.

A type only defines a === method that tells whether the given object is in
the type or not.

class IntType
  def new(range)
    @range = range
  end
  def ===(obj)
    Integer === obj && @range === obj
  end
end

Uint16 = IntType.new(0...2**16)

case x
when Uint16
  # ok
else
  raise TypeError, "#{x} is not a Uint16"
end

> my new class already has so many built-in methods, stuff that 
> I'd want sent to the contained Fixnum gets intercepted.

Do you want to manipulate integer values, or integer variables ?
What does this class do apart from being a Fixnum or a holder thereof?

________________________________________________________________
Mathieu Bouchard                   http://hostname.2y.net/~matju