Hi Luc, Hi all, > [...] > Last week, at work, someone asked me again about differentiation and I > directed him to this issue and also to the Nabla project. He told me he > was interested in having some support in [math] for this (I'm not sure > he reads this list, but if he does, I hope he will join the > discussion). To precise your introduction, I'm working at the french space agency (Cnes) on satellite guidance and attitude. I have to deal with functions like that: public double[] value (double t) { ... } (The best interface for my subjects would be: public Vector3D value (double t) { ... }, but it's not the point now.) > > [...] > > I suggest we deprecate this interface and add a new one defining > method: > > RallNumber value(RallNumber x) > > This interface could extend UnivariateFunction in which case when we > want to compute only the value we use the same object, or it could also > define a getPrimitive method the would return a separate primitive > object (this is how it is done in Nabla, with the interface > UnivariateDerivative > ( bla/core/UnivariateDerivative.html>), > or it can even be completely separate from UnivariateFunction. > > Multivariate differentiable functions or vector valued functions would > be done exactly the same way: replacing the parameter or return value > types from double arrays to RallNumber arrays. This would be much more > consistent than what we currently have (we have methods called > partialDerivatives, gradients, jacobians and even several methods > called > derivative which do not have the same signatures). I'm sorry, I don't understand how it's gonna be for my function : value(double t): double[] I just tried to code the interfaces (UnivariateVectorDifferentiable, UnivariateVectorDerivative, DifferentialPair, UnivariateVectorDifferentiator) and the TwoPointsScheme differentiator. If I get your purpose, DifferentialPair has to contain: - "zero-order": x, f(x) - first order: f(x), f'(x) - second order: f'(x), f''(x) - etc. => What happens for the zero order (x is a double, not an array of double) ? Regards, Julien --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org For additional commands, e-mail: dev-help@commons.apache.org