Re: Math_Function

Hi, Ants Aasma a écrit : > As I see it, a defined function is just an expression with defined > parameter order. Eg. the expression "x+y*z" has parameters/free > variables x,y,z and can be considered to be a function f(x,y,z) = x+y*z. Extending it to expressions would allow equations, and vector/matrix representation (which is not something needed, but it would be a plus). > I'm with you on lightweight, well defined packages, but derivatives > just fit so well into function/operator definition classes. Every > function has a derivative and the derivative is specific to that > function. The overhead, at least now, is minimal - just one relatively > simple function to compile. I don't see any real reason to factor out > that functionality. Knowledge about ones derivative fits very well > into a function definition. Factoring it out creates a parallel > class/logic/information hierarchy, whatever way you implement it, and > that just seems to me as a bad code smell. There is quite a big problem with the design you currently use : its not extensible in functionalities. We're only able to extend the defined functions' list. Adding new functionalities that are function dependent would require a modification of every functions' class. So either we have a Math_Function package that already implements everything (which is not something wanted), either we have an isolated package that is not extensible. Compared to Math_Derivative, the biggest advantage is a good looking design, which doesn't in fact provide many advantages. Talking about a novice user, I think its easier for him to implement a new function just by giving the derivative expression, than having to create a class for it. I think it would be better to consider another design, that would probably contain some parallel class/logic/information that can't IMO be avoided if the goal is to have extensible, small and surgical packages. (quoting Bertrand) > If you have any good ideas how would a derivative operation package > look like with a high-level expression datastructure, I'd love to hear it. Well, I will try to imagine an effective design from a different point of view than yours. And we will compare :) I would really like to have other devs into this thread ! Kind regards, -- Etienne Kneuss http://www.colder.ch/ colder@php.net