[jira] [Commented] (ARROW-15996) [C++] Support casting from time32 and time64 to duration

["David Li (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-15996?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17510461#comment-17510461 ] 

David Li commented on ARROW-15996:
----------------------------------

Does this really make sense? I'm curious how it would help implement other bindings.

> [C++] Support casting from time32 and time64 to duration
> --------------------------------------------------------
>
>                 Key: ARROW-15996
>                 URL: https://issues.apache.org/jira/browse/ARROW-15996
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Dragoș Moldovan-Grünfeld
>            Priority: Critical
>
> It would be really helpful if we could convert {{time32}} and {{time64}} to {{duration}}. For example, it could simplify the implementation of some of the R bindings (e.g. {{difftime}}). 
> {code:r}
> library(arrow, warn.conflicts = FALSE)
> a <- Array$create(32000L)
> a
> #> Array
> #> <int32>
> #> [
> #>   32000
> #> ]
> a$cast(time32())
> #> Array
> #> <time32[ms]>
> #> [
> #>   00:00:32.000
> #> ]
> a$cast(int64())$cast(time64())
> #> Array
> #> <time64[ns]>
> #> [
> #>   00:00:00.000032000
> #> ]
> a$cast(time32())$cast(duration())
> #> Error: NotImplemented: Unsupported cast from time32[ms] to duration using function cast_duration
> a$cast(int64())$cast(time64())$cast(duration())
> #> Error: NotImplemented: Unsupported cast from time64[ns] to duration using function cast_duration
> {code}



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