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Explain meaning of Result iters and link to factory functions #38158

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Dec 21, 2016
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Explain meaning of Result iters and link to factory functions #38158

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29 changes: 26 additions & 3 deletions src/libcore/result.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -501,6 +501,8 @@ impl<T, E> Result<T, E> {

/// Returns an iterator over the possibly contained value.
///
/// The iterator yields one value if the result is [`Ok`], otherwise none.
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Otherwise None (with url).

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Well, no, it doesn't yield None, it just yields no values at all.

I realize this is implemented by next() returning None but I think saying that would only make this confusing. I could rephrase it as "the iterator's next method returns Some of the inner and then None if the result is Ok, otherwise it returns None." But that seems to be needlessly puncturing the iterator abstraction.

A couple of general comments:

  • There are lots of references to well-known types such as None and Ok throughout the code without hyperlinks, indeed even in this very file. If the goal is that every type be manually linked maybe that should go into CONTRIBUTING.md to avoid make that clear. IMO it is not so necessary to linkify values the reader is highly likely to already understand, and that anyhow are linked from nearby.

  • In my experience repeatedly asking contributors for small incremental changes to a PR that's already an improvement tends to discourage future contributions. My normal practice now is to accept the change and encourage them to send another PR making additional cleanups, and I think this gives them a better feeling about contributing.

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@GuillaumeGomez GuillaumeGomez Dec 14, 2016 •
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No, it returns None, not "no values at all".

Also, I'm currently finishing to add missing doc examples, then I'll go through all missing urls. None and every other struct/enum/etc... should be linked.

Also, even it seems minor for you, it isn't for me since all these minor things people don't add, I have to after. And it's getting quite huge.

I don't ask it just to bother you or for extreme and dark reasons, it's really because there is a need out of it.

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Unless I'm misunderstanding it the iter will either have length 1 and contain the value inside the Ok result, or it will have length zero. It never yields None, unless the result is Ok(None). That's what I was trying to say by it yields 'no values at all'.

https://play.rust-lang.org/?gist=3d6a9500b782e878fae356a08888838b&version=stable&backtrace=0

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@GuillaumeGomez GuillaumeGomez Dec 15, 2016 •
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Ok, I see your point. Confusion on my side. Sorry about that... Therefore, no change is needed.

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No problem, I could have been confused myself so I appreciate you checking.

I can send you a little cleanup pr later to linkify other instances. It sure would be nice if we can make it automatic later.

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It's been discussed for a while. You can take a look at this issue if you want to take a look at the current status.

///
/// # Examples
///
/// Basic usage:
Expand All @@ -512,6 +514,8 @@ impl<T, E> Result<T, E> {
/// let x: Result<u32, &str> = Err("nothing!");
/// assert_eq!(x.iter().next(), None);
/// ```
///
/// [`Ok`]: enum.Result.html#variant.Ok
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter(&self) -> Iter<T> {
Expand All @@ -520,6 +524,8 @@ impl<T, E> Result<T, E> {

/// Returns a mutable iterator over the possibly contained value.
///
/// The iterator yields one value if the result is [`Ok`], otherwise none.
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Otherwise None (with url).

///
/// # Examples
///
/// Basic usage:
Expand All @@ -535,6 +541,8 @@ impl<T, E> Result<T, E> {
/// let mut x: Result<u32, &str> = Err("nothing!");
/// assert_eq!(x.iter_mut().next(), None);
/// ```
///
/// [`Ok`]: enum.Result.html#variant.Ok
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter_mut(&mut self) -> IterMut<T> {
Expand Down Expand Up @@ -848,6 +856,8 @@ impl<T, E> IntoIterator for Result<T, E> {

/// Returns a consuming iterator over the possibly contained value.
///
/// The iterator yields one value if the result is [`Ok`], otherwise none.
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Otherwise None (with url).

///
/// # Examples
///
/// Basic usage:
Expand All @@ -861,6 +871,8 @@ impl<T, E> IntoIterator for Result<T, E> {
/// let v: Vec<u32> = x.into_iter().collect();
/// assert_eq!(v, []);
/// ```
///
/// [`Ok`]: enum.Result.html#variant.Ok
#[inline]
fn into_iter(self) -> IntoIter<T> {
IntoIter { inner: self.ok() }
Expand Down Expand Up @@ -893,8 +905,13 @@ impl<'a, T, E> IntoIterator for &'a mut Result<T, E> {

/// An iterator over a reference to the [`Ok`] variant of a [`Result`].
///
/// The iterator yields one value if the result is [`Ok`], otherwise none.
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Otherwise None (with url).

///
/// Created by [`Result::iter`].
///
/// [`Ok`]: enum.Result.html#variant.Ok
/// [`Result`]: enum.Result.html
/// [`Result::iter`]: enum.Result.html#method.iter
#[derive(Debug)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Iter<'a, T: 'a> { inner: Option<&'a T> }
Expand Down Expand Up @@ -934,8 +951,11 @@ impl<'a, T> Clone for Iter<'a, T> {

/// An iterator over a mutable reference to the [`Ok`] variant of a [`Result`].
///
/// Created by [`Result::iter_mut`].
///
/// [`Ok`]: enum.Result.html#variant.Ok
/// [`Result`]: enum.Result.html
/// [`Result::iter_mut`]: enum.Result.html#method.iter_mut
#[derive(Debug)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct IterMut<'a, T: 'a> { inner: Option<&'a mut T> }
Expand Down Expand Up @@ -968,9 +988,12 @@ impl<'a, T> FusedIterator for IterMut<'a, T> {}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<'a, A> TrustedLen for IterMut<'a, A> {}

/// An iterator over the value in a [`Ok`] variant of a [`Result`]. This struct is
/// created by the [`into_iter`] method on [`Result`][`Result`] (provided by
/// the [`IntoIterator`] trait).
/// An iterator over the value in a [`Ok`] variant of a [`Result`].
///
/// The iterator yields one value if the result is [`Ok`], otherwise none.
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Otherwise None (with url).

///
/// This struct is created by the [`into_iter`] method on
/// [`Result`][`Result`] (provided by the [`IntoIterator`] trait).
///
/// [`Ok`]: enum.Result.html#variant.Ok
/// [`Result`]: enum.Result.html
Expand Down