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Add example for iterator_flatten #105034

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Jan 10, 2023
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Add example for iterator_flatten #105034

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76438d2
Add example for iterator_flatten
HintringerFabian Nov 28, 2022
083560b
Add result example + rewording
HintringerFabian Dec 13, 2022
c364d32
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HintringerFabian Jan 9, 2023
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8 changes: 8 additions & 0 deletions library/core/src/iter/traits/iterator.rs
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Expand Up @@ -1495,6 +1495,14 @@ pub trait Iterator {
/// assert_eq!(merged, "alphabetagamma");
/// ```
///
/// Flattening also works on other types like Option and Result:
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It's not really specific to Option or Result though. It's that Flatten doesn't require Item: Iterator, it only needs Item: IntoIterator and Option/Result are types that implement that.

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I think i do not really understand what you mean, should we not add this example should i change it?

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I'm pointing out that "types like Option and Result" is very vague. It doesn't tell the reader which those types have in common so they can be used with Flatten. I don't have a particular improvement in mind, I was just pointing out the vagueness and how it actually works.

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It seems like we already document that "iterator of iterators or an iterator of things that can be turned into iterators" above -- I'm not sure another example is all that useful. I think we have enough examples personally for flatten.

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I think this is okay, although its placement is interrupting the "you can also rewrite this" example below, so we should move this down. For wording, perhaps:

Suggested change
/// Flattening also works on other types like Option and Result:
/// Flattening works on any `IntoIterator` type, including `Option` and `Result`:

Although we're not showing Result, so maybe do so too, or remove that part.

///
/// ```
/// let values = vec![Some(123), Some(321), None, Some(231)];
/// let flattened_values: Vec<_> = values.into_iter().flatten().collect();
/// assert_eq!(flattened_values, vec![123, 321, 231]);
/// ```
///
/// You can also rewrite this in terms of [`flat_map()`], which is preferable
/// in this case since it conveys intent more clearly:
///
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