From: Robert Klemme <bob.news@...>
Date: 2004-09-17T23:49:46+09:00
Subject: Re: Automatic class conversion / function overloading


"Markus" <markus@reality.com> schrieb im Newsbeitrag
news:1095431743.19139.114.camel@lapdog.reality.com...
> On Fri, 2004-09-17 at 06:44, Tore Halvorsen wrote:
>
> > So the ruby way here would be:
> >
> > class Rational
> >   attr_reader :u, :d
> >   def *(o)
> >     case other
> >       when Rational
> >         other = o
> >       when Fixnum
> >         other = Rational.new(o, 1)
> >     end
> >     Rational.new(self.u * other.u, self.d * other.d)
> >   end
> > end
>
> Perhaps.  But (as others have noted) there isn't a single unique ruby
> way.  My ruby way would be more like
>
>
> class Rational
>     attr_reader :u, :d
>     def *(other)
>         other = Rational.new(other, 1) if other.is_a? Fixnum
>         Rational.new(self.u * other.u, self.d * other.d)
>         end
>     end
>
>
>      But as you can see, I even use the old salient-structure
> indentation rules.  Depending on the situation, I might also write:
>
>
> class Fixnum
>     def to_rational
>          Rational.new(self,1)
>          end
>     end
>
> class Rational
>     attr_reader :u, :d
>     def *(other)
>         other = other.to_rational unless other.is_a? Rational
>         Rational.new(self.u * other.u, self.d * other.d)
>         end
>     end
>
> Which would permit types other than Fixnum, provided they implemented
> to_rational.  Taking this to its logical conclusion I would surely then
> rewrite it as:
>
> class Fixnum
>     def to_rational
>          Rational.new(self,1)
>          end
>     end
>
> class Rational
>     attr_reader :u, :d
>     def to_rational
>         self
>         end
>     def *(other)
>         other = other.to_rational
>         Rational.new(self.u * other.u, self.d * other.d)
>         end
>     end
>
> ..which eliminates all class testing and is fairly easily extensible.
> But of course others might have different solutions.
>
> -- MarkusQ

Btw: you know that there are classes Rational, Complex etc. already, do
you?

    robert