[Numpy-discussion] np.diff on boolean arrays now raises

[Sebastian Berg]

On Thu, 2017-06-15 at 22:35 +1200, Ralf Gommers wrote:
> 
> 
> On Thu, Jun 15, 2017 at 7:08 PM, Jaime Fernández del Río <jaime.frio@
> gmail.com> wrote:
> > There is an ongoing discussion on github:
> > 
> > https://github.com/numpy/numpy/issues/9251
> > 
> > In 1.13 np.diff has started raising on boolean arrays, since
> > subtraction of  boolean arrays is now deprecated.
> > 
> > A decision has to be made whether:
> > raising an error is the correct thing to do, and only the docstring
> > needs updating, or
> > backwards compatibility is more important and diff should still
> > work on boolean arrays.
> > 
> 
> The issue is bigger than np.diff. For example, there's a problem with
> the scipy.ndimage morphology functions (https://github.com/scipy/scip
> y/issues/7493) that looks pretty serious. All ndimage.binary_*
> functions (7 of them) for example return boolean arrays, and chaining
> those is now broken. Unfortunately it seems that that wasn't covered
> by the ndimage test suite.
> 
> Possibly reverting the breaking change in 1.13.1 is the best way to
> fix this.
> 

Sure, I would say there is nothing wrong with reverting for now (and it
simply is the safe and easy way).
Though it would be good to address the issue of what should happen in
the future with diff (and possibly the subtract deprecation itself). If
we stick to it, but its necessary, we could delay the deprecation and
make it a VisibleDeprecationWarning.

- Sebastian


> Ralf
> 
> 
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