From: Adam Shelly <adam.shelly@...>
Date: 2008-04-01T03:37:57+09:00
Subject: Re: Modifying FIX::* method

On 3/31/08, Adam Shelly <adam.shelly@gmail.com> wrote:
> On 3/31/08, Alex DeCaria <alex.decaria@millersville.edu> wrote:
> > I want to be able to multiply a NUMERIC object by my Foo object and have
> > it return a new Foo object with all the instance variables multiplied by
> > the Numeric object.
> [...]
> > I'm thinking I have to modify the "*" method for all the subclasses of
> > the NUMERIC class.  Is this correct?  Or am I missing something.
> >
> You don't need to modify Numeric, you just need to tell it how to
> coerce your object into a number.
>

Oops, I didn't read your message closely enough.  Maybe Jason is
right, and you shouldn't even consider doing this, but something like
the following should work:

class Foo
  attr_reader :x,:y
  def initialize(x,y)
    @x=x
    @y=y
  end
  def coerce(n)
    [Foo.new(n,n),self]
  end
  def +(other)
    Foo.new(@x+other.x,@y+other.y)
  end
  def /(other)
    Foo.new(@x/other.x,@y/other.y)
  end

end

p (2 + Foo.new(3,0))  #=> #<Foo:0x27afcb8 @y=2, @x=5>
p f=Foo.new(4,10)      #=> #<Foo:0x27afc68 @y=10, @x=4>
p 100/f                     #=> #<Foo:0x27afbdc @y=10, @x=25>