From: Lenny <kudling@...>
Date: 2003-04-20T02:44:32+09:00
Subject: Adjusting or creating new instance members?

Hi,

in my little Project OPAL (Ordinary PAth Library, www.kudling.de/opal/) i have 
a small problem.

I have a class "Rect", which is defined by two "Point" members "tl" and "tr", 
which itself have the members "x" and "y" each.
Sind "Rect" acts as a bounding box for geometric figures, i want to implement 
a function to Rect, which "adds" a new Point to the bounding box in such a 
way, that the bounding box is enlarged if necessary:

class Rect
                def +( z )
                        if z.kind_of? Point
                                @tl.x = z.x if z.x < @tl.x
                                @tl.y = z.y if z.y > @tl.y
                                @br.x = z.x if z.x > @br.x
                                @br.y = z.y if z.y < @br.y
                                self
                        else
                                # TODO: rect + rect
                        end
                end
end

Now i wonder whether it is better to create new Point members instead of 
adjusting the current member, since when i clone a Rect, the Rect instances 
affect each other. Or is an proper own clone()/copy() funtion preferable?

Thanks
Lenny