tustvold commented on code in PR #7039:
URL: https://github.com/apache/arrow-rs/pull/7039#discussion_r1932365264
##########
arrow-array/src/array/list_array.rs:
##########
@@ -120,8 +120,41 @@ impl OffsetSizeTrait for i64 {
/// (offsets[i], │ ListArray (Array)
/// offsets[i+1]) └ ─ ─ ─ ─
─ ─ ┘ │
/// └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
─ ─ ─ ─ ─
+/// ```
+///
+/// # Slicing
+///
+/// Slicing a `ListArray` creates a new `ListArray` without copying any data,
+/// but this means the Values and Offsets may have "unused" data
///
+/// For exmaple, calling `slice(1, 3)` on the `ListArray` in the above example
Review Comment:
```suggestion
/// For example, calling `slice(1, 3)` on the `ListArray` in the above
example
```
##########
arrow-array/src/array/list_array.rs:
##########
@@ -120,8 +120,41 @@ impl OffsetSizeTrait for i64 {
/// (offsets[i], │ ListArray (Array)
/// offsets[i+1]) └ ─ ─ ─ ─
─ ─ ┘ │
/// └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
─ ─ ─ ─ ─
+/// ```
+///
+/// # Slicing
+///
+/// Slicing a `ListArray` creates a new `ListArray` without copying any data,
+/// but this means the Values and Offsets may have "unused" data
///
+/// For exmaple, calling `slice(1, 3)` on the `ListArray` in the above example
+/// would result in the following. Note
///
+/// 1. `Values` array is unchanged
+/// 2. `Offsets` do not start at `0` nor cover all values in the Values array.
+///
+/// ```text
+/// ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
+/// ┌ ─ ─ ─ ─ ─ ─ ┐
│
+/// │ ╔═══╗ ╔═══╗
+/// │ ║ 1 ║ ║ A ║ │ 0
│
+/// ┌─────────────┐ ┌───────┐ │ ┌───┐ ╔═══╗ ╠═══╣ ╠═══╣
+/// │ [] (empty) │ │ (3,3) │ │ 1 │ ║ 3 ║ │ ║ 1 ║ ║ B ║ │ 1
│
Review Comment:
```suggestion
/// │ [] (empty) │ │ (3,3) │ │ 1 │ ║ 3 ║ │ ║ 1 ║ ║ B ║ │
1 │
```
I'm not sure what the double border is meant to convey, but if it is
"unused" then I think the first offset of `3` probably should be single border
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