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explicitly show how iterating over .. fails #35701

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merged 3 commits into from
Aug 20, 2016
Merged

explicitly show how iterating over .. fails #35701

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377ae44
explicitly show how iterating over `..` fails
matthew-piziak Aug 15, 2016
c186da7
RangeFull for-loop iteration fails because of IntoIterator
matthew-piziak Aug 16, 2016
469b7fd
split example into three sections with explanation
matthew-piziak Aug 18, 2016
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18 changes: 10 additions & 8 deletions src/libcore/ops.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1463,15 +1463,17 @@ pub trait IndexMut<Idx: ?Sized>: Index<Idx> {
/// # Examples
///
/// ```
/// fn main() {
/// assert_eq!((..), std::ops::RangeFull);
/// assert_eq!((..), std::ops::RangeFull);
///
/// let arr = [0, 1, 2, 3];
/// assert_eq!(arr[ .. ], [0,1,2,3]); // RangeFull
/// assert_eq!(arr[ ..3], [0,1,2 ]);
/// assert_eq!(arr[1.. ], [ 1,2,3]);
/// assert_eq!(arr[1..3], [ 1,2 ]);
/// }
/// // for i in .. {
/// // println!("This errors because .. has no IntoIterator impl");
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So, usually rather than commenting the code out, we put things in its own example marked with ignore. And in general, these feel like three separate examples to me. Could you maybe split them up, and put a little sentence between them explaining it?

So for example:

/// The `..` syntax is a `RangeFull`:
///
/// ```
/// assert_eq!((..), std::ops::RangeFull);
/// ```
///
/// It does not have an `IntoIterator` implementation, so you can't use it in a
/// `for` loop directly. This won't compile:
///
/// ```ignore
/// for i in .. {
///    // ...
/// }
/// ```

Something like that? What do you think?

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Yes! I'm thinking that's much better. Will impl. :)

/// // }
///
/// let arr = [0, 1, 2, 3];
/// assert_eq!(arr[ .. ], [0,1,2,3]); // RangeFull
/// assert_eq!(arr[ ..3], [0,1,2 ]);
/// assert_eq!(arr[1.. ], [ 1,2,3]);
/// assert_eq!(arr[1..3], [ 1,2 ]);
/// ```
#[derive(Copy, Clone, PartialEq, Eq, Hash)]
#[stable(feature = "rust1", since = "1.0.0")]
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