[GitHub] [arrow-rs] tustvold commented on a diff in pull request #3144: Add add_mut and add_checked_mut

[GitBox <gi...@apache.org>]

tustvold commented on code in PR #3144:
URL: https://github.com/apache/arrow-rs/pull/3144#discussion_r1028183113


##########
arrow/src/compute/kernels/arity.rs:
##########
@@ -205,6 +205,72 @@ where
     Ok(unsafe { build_primitive_array(len, buffer, null_count, null_buffer) })
 }
 
+/// 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.
+///
+/// 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.
+///
+/// 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
+///
+/// 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.
+pub fn binary_mut<T, F>(
+    a: PrimitiveArray<T>,
+    b: &PrimitiveArray<T>,
+    op: F,
+) -> std::result::Result<

Review Comment:
   As mentioned on #3134 I think this Result should be the other way round



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