[GitHub] [arrow] paleolimbot commented on pull request #13397: ARROW-16444: [R] Implement user-defined scalar functions in R bindings

[GitBox <gi...@apache.org>]

paleolimbot commented on PR #13397:
URL: https://github.com/apache/arrow/pull/13397#issuecomment-1160707504

   All good points and thank you for taking a look! Your edit did the trick, although the segfault may have been due to something about turning a `Scalar` into an `Array`:
   
   ``` r
   # remotes::install_github("apache/arrow/r#13397")
   library(arrow, warn.conflicts = FALSE)
   
   fun <- arrow:::arrow_scalar_function(
     int32(),
     int64(),
     function(x, y) {
       y[[1]]$cast(int64())
     }
   )
   
   arrow:::register_scalar_function("my_test_scalar_function", fun)
   
   # works!
   call_function("my_test_scalar_function", Array$create(1L))
   #> Array
   #> <int64>
   #> [
   #>   1
   #> ]
   
   # segfaults!
   # call_function("my_test_scalar_function", Scalar$create(1L))
   ```
   
   <sup>Created on 2022-06-20 by the [reprex package](https://reprex.tidyverse.org) (v2.0.1)</sup>
   
   > you will get a test failure saying the function is already registered
   
   It seems there's no way to unregister a function...if there were, I could unregister it in the test. I changed the `AddFunction()` call to overwrite the existing function for now but that's probably not a good long-term choice.
   
    


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