[GitHub] [arrow] jonkeane commented on pull request #10724: ARROW-12964: [R] Add bindings for ifelse() and if_else()

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jonkeane commented on pull request #10724:
URL: https://github.com/apache/arrow/pull/10724#issuecomment-880871906


   Ok, I've pushed a few changes. The biggest one is that I've removed the `assert_that` call (since it wasn't quite what we wanted) and am not relying on the kernel dispatch to tell us if we have incompatible types.
   
   We might want to have our own type checking, but it's not totally trivial with what we have now. We have some of the `is.*` methods after https://issues.apache.org/jira/browse/ARROW-12781, though for this what we really need is something like an extension of `typeof()` for expressions that return the type and then a function that compares those types + the R types and their arrow mappings to ensure that those are compatible. I think this is out of the scope for this PR (and might actually be deferrable until https://issues.apache.org/jira/browse/ARROW-13186 is done or possibly forever).
   
   We don't support `ifelse`'s autocasting abilities — I'm hesitant to even try since it's not a particularly stable or good behavior, though I wish there was a way we could message or warn explaining that / why we did that. 


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