Hash

[MarcinKonowalczyk]

What do these changes do?

Added __hash__ to FrozenList. Normal python lists are not hashable. FrozenList is hashable only when it is frozen, otherwise it throws a RuntimeError.

Are there changes in behavior for the user?

Frozen FrozenLists can now be used as dictionary keys.

Related issue number

N/A.

Checklist

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[mjpieters]

Hi 👋

Thank you for contributing a pull request 👍 In principle this is a good addition. But note that:

• __hash__ should raise TypeError when not frozen
• you’ll also need to provide a Cython implementation, see frozenlist/_frozenlist.pyx

[MarcinKonowalczyk]

I've added the Cython support. I disagree, however, that the hash of an unfrozen list ought to throw a TypeError. FrozenList is hashable (therefore it's not of the wrong type), it's just that it is an error if one attempts to hash it if it has not been frozen.

[mjpieters]

I've added the Cython support. I disagree, however, that the hash of an unfrozen list ought to throw a TypeError. FrozenList is hashable (therefore it's not of the wrong type), it's just that it is an error if one attempts to hash it if it has not been frozen.

Thinking about this again, you are right. Thanks for adding this!