Add a range argument to vec.extract_if #133265
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| /// ``` | ||
| /// #![feature(extract_if)] | ||
| /// let mut items = vec![0, 0, 0, 0, 0, 0, 0, 1, 2, 1, 2, 1, 2]; | ||
| /// let ones = items.extract_if(7.., |x| *x == 1).collect::<Vec<_>>(); |
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Maybe change one of the first few 0s to 1 to indicate they don't get extracted (out of range)?
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Hrm, I wanted to show the "I have a prefix that I know doesn't contain those things, so I can skip them" use.
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r? @cuviper (sorry, I didn't realize this was assigned to me)
Since this is a pretty significant API and implementation change, maybe it would be good to hold off for a couple of weeks? In case anyone using this API unstably has feedback after the change (I doubt it, but doesn't hurt). |
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Changing and stabilizing in the same PR doesn't seem ideal to me either, especially when the change happened parallel to the FCP. I think it should bake a few days at least. |
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@bors r+ |
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Indeed, fixed. @bors r=cuviper |
| /// ``` | ||
| /// # use std::cmp::min; | ||
| /// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 }; | ||
| /// # let mut vec = vec![1, 2, 3, 4, 5, 6]; |
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Apologies for the late comment, but I wanted to point out that this sample code doesn't behave the same way as the real extract_if(). Given the same predicate and range, if your vector were [1, 2, 3, 3, 3, 3, 3, 3, 4, 5, 6], then all of the 3s would be removed. i is only incremented when an element is dropped, but range.end is unchanged, so the items shift down. I got very confused when reading the docs and trying to square this sample code with the explanation of how the function works.
Fortunately, the real extract_if() does not have this problem. Proposed change to the sample code:
let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 5 };
let mut vec = vec![0, 1, 2, 3, 4, 5, 6];
let range = 1..5;
let mut i = range.start;
let mut end = range.end;
while i < min(vec.len(), end) {
if some_predicate(&mut vec[i]) {
let _val = vec.remove(i);
end -= 1;
// your code here
} else {
i += 1;
}
}
assert_eq!(vec, vec![0, 1, 4, 5, 6]);There was a problem hiding this comment.
If you want to propose a documentation improvement you can just open a PR.
tracking issue: #43244
This adds the range argument requested in #43244 (comment)