From: Markus <markus@...>
Date: 2004-09-17T23:36:51+09:00
Subject: Re: Automatic class conversion / function overloading

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