[C++] Implement power / exponentiation compute kernel

[asfimport]

We have addition, subtraction, multiplication, and division.

Reporter: Jonathan Keane / @jonkeane
Assignee: Rok Mihevc / @rok

Related issues:

• [C++] Arithmetic kernels for numeric arrays (is a child of)
• [C++] Add element-wise power() compute function (duplicates)

PRs and other links:

• GitHub Pull Request #9841

_{Note: This issue was originally created as ARROW-11070. Please see the migration documentation for further details.}

[asfimport]

Jonathan Keane / @jonkeane:
ARROW-11428 may be relevant (though is only implemented in the Rust client there)

[asfimport]

Antoine Pitrou / @pitrou:
The Rust and C++ implementations are entirely distinct, so ARROW-11428 is irrelevant here.

[asfimport]

Joris Van den Bossche / @jorisvandenbossche:
Copying my note about null behaviour from ARROW-11871:

One behavioural aspect that has come up in pandas is the question about what to do with nulls in case of power(null, 0) or power(1, null): propagate the null value (as is otherwise always done for element-wise arithmetic operations), or in this case return an actual result (1 in both cases, in the idea that whathever value the null might represent, the result is always 1). Reference to the pandas issue: pandas-dev/pandas#29997. It seems that eg R (return 1) and SQL (propagate null) have different behaviour on this aspect. So if we want to support both use cases, an option to switch might be needed.

[asfimport]

Neal Richardson / @nealrichardson:
Issue resolved by pull request 9841
#9841