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Gilles commented on MATH-373: ----------------------------- IIRC, changing the package name had been suggested and discussed for 2.0. [One argument is that, to be consistent, you'd have to change the name at every major release...] > StatUtils.sum returns NaN for zero-length arrays > ------------------------------------------------ > > Key: MATH-373 > URL: https://issues.apache.org/jira/browse/MATH-373 > Project: Commons Math > Issue Type: Bug > Affects Versions: 2.1 > Reporter: Roman Werpachowski > Fix For: 3.0 > > > StatUtils.sum returns NaN for zero-length arrays, which is: > 1. inconsistent with the mathematical notion of sum: in maths, > sum_{i=0}^{N-1} a_i will be 0 for N=0. In particular, the identity > sum_{i=0}^{k-1} a_i + sum_{i=k}^{N-1} = sum_{i=0}^{N-1} > is broken for k = 0, since NaN + x = NaN, not x. > 2. introduces hard to debug erros (returning a NaN is one of the worst forms > of reporting an exceptional condition, as NaNs propagate silently and require > manual tracing during the debugging) > 3. enforces "special case" handling when the user expects that the summed > array can have a zero length. > The correct behaviour is, in my opinion, to return 0.0, not NaN in the above > case. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.