On 06/01/07, Timothy Hochberg <[EMAIL PROTECTED]> wrote: > Do we have to revisit that thread? I seem to recall it getting kind of > cranky. To avoid reliving that, I will attempt dredge up the relevant issue: > > "a[indx]+=b" should be the same as "a[indx]=a[indx]+b". All else follow from > that. If staring at that for a while doesn't enlighten you, then you will > have to read that thread.
I'm afraid I dredged this issue up previously, and I have no desire to do so again, but this is not an identity: In [3]: a = arange(5) In [4]: a[1:] = a[1:] + a[:-1] In [5]: a Out[5]: array([0, 1, 3, 5, 7]) In [6]: a = arange(5) In [7]: a[1:] += a[:-1] In [8]: a Out[8]: array([ 0, 1, 3, 6, 10]) In fact the python documentation simply states that the two should be "nearly identical". However, a subtler restriction, explained to me by Robert Kern (http://aspn.activestate.com/ASPN/Mail/Message/scipy-user/3257570), means that it is in basically infeasible and inappropriate to make this do what I would have wanted it to. Nothing, of course, prevents anyone from implementing this in a function; in fact I think some of the histogram functions are capable of efficiently doing the most common things one might want this for. A. M. Archibald A. M. Archibald _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
