jorisvandenbossche commented on a change in pull request #10016:
URL: https://github.com/apache/arrow/pull/10016#discussion_r613842949
##########
File path: cpp/src/arrow/compute/kernels/scalar_arithmetic.cc
##########
@@ -233,6 +235,43 @@ struct DivideChecked {
}
};
+struct Negate {
+ template <typename T, typename Arg0>
+ // NOTE [EPM]: Discuss on 0 vs. -0.
+ static constexpr enable_if_floating_point<T> Call(KernelContext*, Arg0 arg) {
+ return -arg;
+ }
+
+ // NOTE [EPM]: How to handle unsigned integers?
+ // * Promote to signed?
+ // * State that unsigned numbers are not supported (i.e., undefined
behavior)?
+ // * Use C++ integral conversions (e.g., Negate(-128) = -128)?
Review comment:
For reference, numpy preserves the dtype for unsigned integers:
```
In [14]: arr = np.array([0, 255], dtype="uint8")
In [15]: -arr
Out[15]: array([0, 1], dtype=uint8)
In [16]: np.negative(arr)
Out[16]: array([0, 1], dtype=uint8)
```
(not sure that's very useful, though)
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