From: Ralph Aichinger <ralph@...>
Date: 2004-06-27T22:43:02+09:00
Subject: Newbie: How to model this?

Please be kind, this is probably a completely dumb newbie question,
but I just finished reading the Thomas/Hunt book and have basically
no previous experience with truely object-oriented programming:

How do I do the following in a elegant fashion?

I want to work with an object describing geographical coordinates 
as you can read them from a GPS.

At least I need the longitude, latitude and height of the point
as an instance variable, as far as I can see. So far so good:

class Location
  def initialize(lon,lat,hgt)
    @lon = lon
    @lat = lat
    @hgt = hgt
  end
end

Latitude and longitude are basically angles, which can be described
in degrees, minutes and seconds or decimal degrees, and a number
of other formats.

I want methods like myPoint.dmsdegrees giving just the degrees
part of myPoint in degree, minute, second format. These should be
"virtual attributes" if I understand Thomas/Hunt right.

How can I define this in the most elegant fashion? I cannot let Location
inherit this from a base class "Angle" with all these conversion
methods, can I, because a Location is not a Angle, at least not just
a Angle.

Of course I could just code these conversion methods twice (once for
lat, once for lon) for each conversion in the body of the class
"Location". However I think there *must* be a better method than 
this copy&paste techniqe.

TIA
/ralph