Improve Iterator::by_ref example
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I split the example into two: one that fails to compile, and one that works. I also made them identical except for the addition of `by_ref` so we don't confuse readers with random differences.
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(rust-highfive has picked a reviewer for you, use r? to override) |
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Might as well just r? @steveklabnik |
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Jan 8, 2021
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| /// This demonstrates a use case that needs `by_ref`: | ||
| /// | ||
| /// ```compile_fail,E0382 | ||
| /// let a = [1, 2, 3, 4, 5]; | ||
| /// let mut iter = a.iter(); | ||
| /// | ||
| /// let sum: i32 = iter.take(3).fold(0, |acc, i| acc + i); | ||
| /// assert_eq!(sum, 6); | ||
| /// | ||
| /// // if we try to use iter again, it won't work. The following line | ||
| /// // gives "error: use of moved value: `iter` | ||
| /// // assert_eq!(iter.next(), None); | ||
| /// // Error! We can't use `iter` again because it was moved | ||
| /// // by `take`. | ||
| /// assert_eq!(iter.next(), Some(&4)); | ||
| /// ``` | ||
| /// | ||
| /// // let's try that again | ||
| /// let a = [1, 2, 3]; | ||
| /// Now, let's use `by_ref` to make this work: | ||
| /// | ||
| /// ``` | ||
| /// let a = [1, 2, 3, 4, 5]; | ||
| /// let mut iter = a.iter(); | ||
| /// | ||
| /// // instead, we add in a .by_ref() | ||
| /// let sum: i32 = iter.by_ref().take(2).fold(0, |acc, i| acc + i); | ||
| /// | ||
| /// assert_eq!(sum, 3); | ||
| /// // We add in a call to `by_ref` here so `iter` isn't moved. | ||
| /// let sum: i32 = iter.by_ref().take(3).fold(0, |acc, i| acc + i); | ||
| /// assert_eq!(sum, 6); | ||
| /// | ||
| /// // now this is just fine: | ||
| /// assert_eq!(iter.next(), Some(&3)); | ||
| /// assert_eq!(iter.next(), None); | ||
| /// // And now we can use `iter` again because we still own it. | ||
| /// assert_eq!(iter.next(), Some(&4)); | ||
| /// ``` |
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At this point, should I just remove the later example? I don't feel like it adds much that the basic usage example doesn't show.
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@camelid do youw ant to update this without the last example? looks good enough to me without it
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@Dylan-DPC OK, I removed the example. Do you want to review this now?
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i could review it, but i would prefer @steveklabnik to have a final look at it |
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This looks reasonable to me. |
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Looks good to me, thanks! @bors: r+ rollup |
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📌 Commit 49ccc3f has been approved by |
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Rollup of 11 pull requests Successful merges: - rust-lang#80805 (Improve `Iterator::by_ref` example) - rust-lang#84248 (Remove duplicated fn(Box<[T]>) -> Vec<T>) - rust-lang#84321 (rustdoc: Convert sub-variant toggle to HTML) - rust-lang#84359 (:arrow_up: rust-analyzer) - rust-lang#84374 (Clean up .gitignore) - rust-lang#84387 (Move `sys_common::poison` to `sync::poison`) - rust-lang#84430 (doc/platform-support: clarify UEFI support) - rust-lang#84433 (Prevent control, shift and alt keys to make search input lose focus) - rust-lang#84444 (doc: Get rid of "[+] show undocumented items" toggle on numeric From impls) - rust-lang#84456 (Fix ICE if original_span(fn_sig) returns a span not in body sourcefile) - rust-lang#84469 (Update comment on `PrimTy::name_str`) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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I split the example into two: one that fails to compile, and one that
works. I also made them identical except for the addition of
by_refso we don't confuse readers with random differences.
cc @steveklabnik, who is the one that added the previous version of this example