tustvold commented on code in PR #5798:
URL: https://github.com/apache/arrow-rs/pull/5798#discussion_r1613559421
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arrow-arith/src/arity.rs:
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@@ -207,23 +227,46 @@ where
Ok(PrimitiveArray::new(buffer.into(), nulls))
}
-/// Given two arrays of length `len`, calls `op(a[i], b[i])` for `i` in
`0..len`, mutating
-/// the mutable [`PrimitiveArray`] `a`. If any index is null in either `a` or
`b`, the
-/// corresponding index in the result will also be null.
+/// Applies a binary and infallible function to values in two arrays, replacing
+/// the values in the first array in place.
///
-/// Mutable primitive array means that the buffer is not shared with other
arrays.
-/// As a result, this mutates the buffer directly without allocating new
buffer.
+/// # Details
+///
+/// Given two arrays of length `len`, calls `op(a[i], b[i])` for `i` in
+/// `0..len`, modifying the [`PrimitiveArray`] `a` in place, if possible.
+///
+/// If any index is null in either `a` or `b`, the corresponding index in the
+/// result will also be null.
+///
+/// # Buffer Reuse
+///
+/// If the underlying buffers in `a` are not shared with other arrays, mutates
+/// the underlying buffer in place, without allocating.
///
/// Like [`unary`] the provided function is evaluated for every index,
ignoring validity. This
/// is beneficial when the cost of the operation is low compared to the cost
of branching, and
/// especially when the operation can be vectorised, however, requires `op` to
be infallible
/// for all possible values of its inputs
///
-/// # Error
+/// # Errors
///
-/// This function gives error if the arrays have different lengths.
-/// This function gives error of original [`PrimitiveArray`] `a` if it is not
a mutable
-/// primitive array.
+/// * if the arrays have different lengths.
+///
+/// # See Also
+///
+/// * Documentation on [`PrimitiveArray::unary_mut`] for operating on
[`ArrayRef`].
+///
+/// # Example
+/// ```
+/// # use arrow_arith::arity::binary_mut;
+/// # use arrow_array::Float32Array;
+/// # use arrow_array::types::Int32Type;
+/// let a = Float32Array::from(vec![Some(5.1f32), None, Some(6.8)]);
+/// let b = Float32Array::from(vec![Some(1.0f32), None, Some(2.0)]);
+/// // compute a + b, updating the value in a in place if possible
+/// let a = binary_mut(a, &b, |a, b| a + b).unwrap().unwrap();
Review Comment:
The wrapped Result is necessary to distinguish between an error taking
ownership and an error performing the computation.
As for the different types, that is likely just an oversight
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