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From Gilles Sadowski <>
Subject Re: [Math] PolynomialFunctionLagrangeForm (continued)
Date Sun, 31 Oct 2010 16:59:36 GMT
On Sun, Oct 31, 2010 at 03:57:33PM +0100, Luc Maisonobe wrote:
> Le 31/10/2010 15:08, Gilles Sadowski a écrit :
> > Hi.
> > 
> > [Continued from the previous message.]
> > 
> > Accepting that the interpolation abscissae are not sorted in strictly
> > increasing order make it necessary to check (at every call to the "value"
> > method) that no 2 interpolating points are the same.
> > The code would be cleaner is we assume (as a pre-condition) that the "x"
> > interval is sorted. [And it would be more similar to other interpolating
> > classes that explicitely prohibit unsorted interpolation intervals.]
> So I guess you would put this check in the verifyInterpolationArray
> method which is called from constructor and remove the d == 0 check in
> computeCoefficient ?


> Beware that the static evaluate method can be called directly from
> outside. We need to keep this public method, so we may perhaps split it
> as a check followed by a call to a private internal method that does no
> check, whereas the value instance method would directly call the
> no-check version since the check would have been done beforehand in the
> constructor.

This is exactly what I've already implemented.
What remains is the "problem" of allowing unsorted input arrays.

> > 
> > If we nevertheless want to allow the user to pass an unsorted interval, I'd
> > rather have a new utility method that would sort the "x" interval (and apply
> > the corresponding permutations to "y") within the constructor.

So, what do you think of just require that the array be sorted?
[This would imply changing the test, where the array is not sorted.]


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