Re: Clean Object Class Design -- Circle/Ellipse

having a master of science in theoretical mathematics, perhaps some would agree that i may provide an informed perspective on the topics at hand.

first, wrt two dimensional geometries, there are really only two kinds: closed curves and open curves. any closed curve can be mapped into any other closed curves by applying some function(s); ie, all closed curves are isomorphic. similarly, all open curves are isomorphic. it makes no difference what you choose to label your closed curve... it is just an alternative representation of any other closed curve. there are well known proofs of these statements.

second, wrt classes, whether or not one subclasses one from the other just depends. it may or may not be useful. this is a design decision to be made by a "hopefully" informed application architect or developer. it might even be more useful to begin with the actual mathematical definitions, ie, two dimensional entities (2De). then sublcass into 2De-open and 2De-closed. open curves has well defined functions, such as slope, intercept, rate of change (d f(x) = dx), etc. similarly closed curves have common properties such as perimeter, area, centers, etc... as for the practicality of doing this, again, it just depends... are you writing a mathematical application or just trying to simplify geometires commonly used... rectangle, square, circle, elipse, trapezoid, rhombus, etc... [of course, these could be derived from parallelograms].

unless there is a clear understanding of the scope and nature of the project, one has a hard time making a determination as to which approach is optimal. one even must take into account the performance characteristics of the programming language and platforms. for example, while Ada is very flexible wrt generic classes and generic instantations as well as subclassing, etc, it is a resource hog, as is java. the dependencies in Ada results in minor chagnes in the original base class or significantly distant ancestors a major effort to recomplie (the entire application).

just my $0.02g Received on Tue Aug 21 2001 - 01:10:33 CEST