Add transpose conversions for nested Option and Result
These impls are useful when working with combinator
methods that expect an option or a result, but you
have a `Result<Option<T>, E>` instead of an `Option<Result<T, E>>`
or vice versa.
Standardize on "re-export" rather than "reexport"
While working on the book with our editors, it was brought to our attention that we're not consistent with when we use "re-export" versus "reexport". For the book, we've decided (with our editors) to go with "re-export"; in prose, I think that looks better. In code, I'm fine with "reexport".
However, the rustdoc generated section is currently "Reexports", so when we have a screenshot of generated documentation with the prose where we use "re-export", it's inconsistent.
It's too late to fix this for the book because we're using 1.21.0 for the output in the book, and it's really only one spot so it's not a huge deal, but I'd like to advocate for changing the documentation header so that a future edition of the book can be consistent.
The first commit here only changes the documentation section heading text and rustdoc documentation that references it. This is the commit that's most important to me.
The second commit changes error messages and associated tests to also be consistent with the use of re-export. This is the next most important commit to me, but I could be argued out of this one because then it won't match code like the `macro_reexports` feature name, which ostensibly should change to `macro_re_exports` to be most consistent but I didn't want to change code.
The last commit changes re-export anywhere else in prose: either in documentation comments or regular comments. This is least important as most of them aren't user-visible. Instances like these will likely sneak back in over time. I'm totally fine dropping this commit if anyone wants, but [the hobgoblins made me do it](http://www.bartleby.com/100/420.47.html) and it sets a good example.
r? @steveklabnik
Add slice::ExactChunks and ::ExactChunksMut iterators
These guarantee that always the requested slice size will be returned
and any leftoever elements at the end will be ignored. It allows llvm to
get rid of bounds checks in the code using the iterator.
This is inspired by the same iterators provided by ndarray.
Fixes https://github.com/rust-lang/rust/issues/47115
I'll add unit tests for all this if the general idea and behaviour makes sense for everybody.
Also see https://github.com/rust-lang/rust/issues/47115#issuecomment-354715511 for an example what this improves.
No longer parse it.
Remove AutoTrait variant from AST and HIR.
Remove backwards compatibility lint.
Remove coherence checks, they make no sense for the new syntax.
Remove from rustdoc.
- Simplify nth() by making use of the fact that the slice is evenly
divisible by the chunk size, and calling next() instead of
duplicating it
- Call next_back() in last(), they are equivalent
- Implement ExactSizeIterator::is_empty()
These guarantee that always the requested slice size will be returned
and any leftoever elements at the end will be ignored. It allows llvm to
get rid of bounds checks in the code using the iterator.
This is inspired by the same iterators provided by ndarray.
See https://github.com/rust-lang/rust/issues/47115
Add iterator method specialisations to Range*
Add specialised implementations of `max` for `Range`, and `last`, `min` and `max` for `RangeInclusive`, all of which lead to significant advantages in the generated assembly on x86.
Note that adding specialisations of `min` and `last` for `Range` led to no benefit, and adding `sum` for `Range` and `RangeInclusive` led to type inference issues (though this is possibly still worthwhile considering the performance gain).
This addresses some of the concerns in #39975.
These impls are useful when working with combinator
methods that expect an option or a result, but you
have a Result<Option<T>, E> instead of an Option<Result<T, E>>
or vice versa.
Deprecate [T]::rotate in favor of [T]::rotate_{left,right}.
Background
==========
Slices currently have an **unstable** [`rotate`] method which rotates
elements in the slice to the _left_ N positions. [Here][tracking] is the
tracking issue for this unstable feature.
```rust
let mut a = ['a', 'b' ,'c', 'd', 'e', 'f'];
a.rotate(2);
assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);
```
Proposal
========
Deprecate the [`rotate`] method and introduce `rotate_left` and
`rotate_right` methods.
```rust
let mut a = ['a', 'b' ,'c', 'd', 'e', 'f'];
a.rotate_left(2);
assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);
```
```rust
let mut a = ['a', 'b' ,'c', 'd', 'e', 'f'];
a.rotate_right(2);
assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']);
```
Justification
=============
I used this method today for my first time and (probably because I’m a
naive westerner who reads LTR) was surprised when the docs mentioned that
elements get rotated in a left-ward direction. I was in a situation
where I needed to shift elements in a right-ward direction and had to
context switch from the main problem I was working on and think how much
to rotate left in order to accomplish the right-ward rotation I needed.
Ruby’s `Array.rotate` shifts left-ward, Python’s `deque.rotate` shifts
right-ward. Both of their implementations allow passing negative numbers
to shift in the opposite direction respectively. The current `rotate`
implementation takes an unsigned integer argument which doesn't allow
the negative number behavior.
Introducing `rotate_left` and `rotate_right` would:
- remove ambiguity about direction (alleviating need to read docs 😉)
- make it easier for people who need to rotate right
[`rotate`]: https://doc.rust-lang.org/std/primitive.slice.html#method.rotate
[tracking]: https://github.com/rust-lang/rust/issues/41891
doc: improve None condition doc for `checked_div` and `checked_rem`
This commit improves the condition mentioned in the docs for which `checked_div` and `checked_rem` return `None`.
For signed division, the commit changes "the operation results in overflow" to "the division results in overflow", otherwise there is room for misinterpretation for `checked_rem`: Without considering overflow, `MIN % -1` would be simply zero, allowing the misinterpretation that "the operation" does not result in overflow in this case. This ambiguity is removed using "when the division results in overflow".
For unsigned division, the condition for `None` should be simply when `rhs == 0`, as no other overflow is possible.
Bump to 1.25.0
* Bump the release version to 1.25
* Bump the bootstrap compiler to the recent beta
* Allow using unstable rustdoc features on beta - this fix has been applied to
the beta branch but needed to go to the master branch as well.
Equivalent example for ? operator
The example with the ? operator in the documentation for try! macro was missing file.write_all.
Now all three examples are consistent.
Correct a few stability attributes
* The extra impls for `ManuallyDrop` were added in #44310 which was only stabilised in 1.22.0.
* The impls for `SliceIndex` were stabilised in #43373 but as `RangeInclusive` and `RangeToInclusive` are still unstable the impls should remain unstable.
* The `From` impls for atomic integers were added in #45610 but most atomic integers are still unstable.
* The `shared_from_slice2` impls were added in #45990 but they won't be stable until 1.24.0.
* The `Mutex` and `RwLock` impls were added in #46082 but won't be stable until 1.24.0.
* Bump the release version to 1.25
* Bump the bootstrap compiler to the recent beta
* Allow using unstable rustdoc features on beta - this fix has been applied to
the beta branch but needed to go to the master branch as well.
