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https://issues.apache.org/jira/browse/ARROW-15455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17566983#comment-17566983
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Jabari Booker commented on ARROW-15455:
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Because the compute component of Arrow is not apart of core, we cannot call
make calls to {{Cast()}} in {{Scalar::CastTo()}} . Therefore, we would need to
reimplement casting to get {{Scalar::CastTo()}} work between list-type scalars.
This is only impacts {{scalar.cast()}} in PyArrow. I was wondering if this
effort seems at all worth it considering you simply use {{pc.cast()}} anyways.
> [C++] Cast between fixed size list type and variable size list
> ---------------------------------------------------------------
>
> Key: ARROW-15455
> URL: https://issues.apache.org/jira/browse/ARROW-15455
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Joris Van den Bossche
> Assignee: Jabari Booker
> Priority: Major
> Labels: good-second-issue, kernel, pull-request-available
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Casting from fixed size list to variable size list could be possible, I
> think, but currently doesn't work:
> {code:python}
> >>> fixed_size = pa.array([[1, 2], [3, 4]], type=pa.list_(pa.int64(), 2))
> >>> fixed_size.cast(pa.list_(pa.int64()))
> ...
> ArrowNotImplementedError: Unsupported cast from fixed_size_list<item:
> int64>[2] to list using function cast_list
> {code}
> And in principle, a cast the other way around could also be possible if it is
> checked that each list has the correct length.
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