abreis edited a comment on pull request #9454:
URL: https://github.com/apache/arrow/pull/9454#issuecomment-777809399
IMO, that would be the superior approach (though it's a much larger rewrite).
I tried to mock what it could look like for the numeric kernels:
```rust
// Datum with concrete types for the arithmetic module
enum DatumNumeric<'a, T>
where
T: ArrowNumericType,
{
Array(&'a PrimitiveArray<T>),
Scalar(T::Native),
}
// lets the user pass arrays without interacting with Datum
impl<'a, T> From<&'a PrimitiveArray<T>> for DatumNumeric<'a, T>
where
T: ArrowNumericType,
{
fn from(array: &'a PrimitiveArray<T>) -> Self {
DatumNumeric::Array(array)
}
}
// can match and run specialized code for array/array, array/scalar, etcetera
fn datum_math_divide<'a, T, DN>(left: DN, right: DN) ->
Result<PrimitiveArray<T>>
where
T: ArrowNumericType,
T::Native: Div<Output = T::Native> + Zero,
DN: Into<DatumNumeric<'a, T>>,
{
use DatumNumeric::*;
match (left.into(), right.into()) {
(Array(left), Array(right)) => todo!("array/array"),
(Array(array), Scalar(divisor)) => todo!("array/scalar"),
_ => todo!(),
}
}
fn test_datum_divide() {
let a = Int32Array::from(vec![15, 15, 8, 1, 9]);
let b = Int32Array::from(vec![5, 6, 8, 9, 1]);
let c = datum_math_divide(&a, &b).unwrap(); // Works, same interface as
before
}
```
However, Rust doesn't like the impl From for scalars (I tried ` impl<'a, T>
From<T::Native> for DatumNumeric<'a, T> where T: ArrowNumericType`). Perhaps
there's a better way to accomplish this.
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