Commits on Sep 22, 2024

1. Fix __eq__ and __ne__ for classes implementing them …

   Main issue, which concerns Vector, Location, and ShapeList:
   
   Comparison with an object of a different type should not cause an
   exception - they are simply not equal. Raising an exception in __eq__
   can (and will*) break unrelated code that expects __eq__ to be well-behaved.
   
   (* I noticed this bug when cq-editor choked on it while trying to find
      a name for an object in a dictionary of local variables)
   
   There's a second more minor issue, which concerns the rest of the classes:
   
   When the other type in __eq__ is not supported, one should technically
   return NotImplemented instead of False, to allow the other type to take
   part in the comparison, in case they know about our type.
   
   (__ne__ should also not generally be implemented as just the negation of
   __eq__ because of this, but that's also a moot point because the __ne__
   can just be removed - Python will automatically do the right thing based
   on __eq__ here)
   
   Technically, the __eq__ for Vector and Plane is also broken in another way:
   It's not transitive.
   
   >>> a, b, c = Vector(0), Vector(9e-6), Vector(18e-6)
   >>> a == b == c
   True
   >>> a == c
   False
   
   They should really eg. have a separate is_close() for approximate comparison,
   but this isn't fixed here, since I have no idea how many places it'd break,
   for one.

   

   alexer committed Sep 22, 2024
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