Region.EMPTY instead of None
#624
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drothlis
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Jun 12, 2022
`None` means an empty region, for example the result of `Region.intersect` if the input regions don't overlap. We can handle `None` on either side of the operator, by implementing the reflected operators (`__radd__` and `__rsub__`). See https://docs.python.org/3/reference/datamodel.html#object.__radd__ We still can't support `None + None` but that's a limitation I can live with for now. Fixing this properly will require adding a new singleton to represent empty regions, changing `Region.intersect` to return that instead of `None`, and updating the implementation of all our other region-handling code. There's a (out of date) pull request for that: #624
Yes,
0, I think.
EMPTY, definitely better. |
Interesting. That's still true as of Python 3.10.5. |
drothlis
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None as Region with Region.NONERegion.EMPTY instead of None
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I think this is a bit neater.
This may make it easier to use functions that return a `Region` that might be `None` because in many cases they may not need to check `region is None` before performing operations on that region. It also makes it easier to implement functions with take a default `Region` because we can follow the standard `region is not None` to mean "did the caller pass a region argument". For an example of this see `Grid`.
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Rebased on master to resolve conflicts. |
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This may make it easier to use functions that return a
Regionthat mightbe
Nonebecause in many cases they may not need to checkregion is Nonebefore performing operations on that region. It also makes it easier to
implement functions with take a default
Regionbecause we can follow thestandard
region is not Noneto mean "did the caller pass a regionargument". For an example of this see
Grid.I don't think this should go in the next release. It would be better to let it bake for a while.
TODO:
Region.NONE == Region.NONE? CurrentlyRegion.NONE == Region.NONE, butRegion.NONE != Region(float('nan'), float('nan'), float('nan'), float('nan'))becauseNAN != NANandNAN != float('nan')but(NAN,) == (NAN,)and(NAN,) != (float('nan'))Region.NONE.width == 0ornan?, equally for heightNONEa good name? PerhapsEMPTYwould be better?NoneasRegionin our codebase.