HaoYang670 commented on code in PR #1577:
URL: https://github.com/apache/arrow-rs/pull/1577#discussion_r852073252
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arrow/src/compute/kernels/substring.rs:
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@@ -59,13 +78,14 @@ fn generic_substring<OffsetSize: StringOffsetSizeTrait>(
let mut len_so_far = zero;
new_offsets.push(zero);
- offsets.windows(2).for_each(|pair| {
- let new_start = cal_new_start(pair[0], pair[1]);
- let new_length = cal_new_length(new_start, pair[1]);
- len_so_far += new_length;
- new_starts_ends.push((new_start, new_start + new_length));
+ offsets.windows(2).try_for_each(|pair| -> Result<()> {
Review Comment:
The reasons that I use `dyn Fn` are:
1. We should do the comparison for `start` and the destruction for `length`
outside the for loop. And using closure is a convenient way, otherwise there
would be lots of duplicate code.
2. Closures have different sizes because they capture different environment.
3. The dynamic dispatching doesn't impact the performance in this function
because they are not hotspots.
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