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and add one for non-mut slicing since I touched that method too
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This commit tweaks a few stable APIs in the `beta` branch before they hit
stable. The `str::is_whitespace` and `str::is_alphanumeric` functions were
deleted (added in #49381, issue at #49657). The `and_modify` APIs added
in #44734 were altered to take a `FnOnce` closure rather than a `FnMut` closure.
Closes #49581
Closes #49657
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94d1970bba87f2d2893f6e934e4c3f02ed50604d moved the alloc::allocator
module to core::heap, moving e.g. Alloc and Layout out of the alloc
crate. While alloc::heap reexports them, it's better to use them from
where they really come from.
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Move the alloc::allocator module to core::heap
This is the `Alloc` trait and its dependencies.
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Remove unnecessary use core::hash in liballoc/boxed.rs
It' only used for hash::Hasher, but Hasher is also imported.
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Use f{32,64}::to_bits for is_zero test in vec::SpecFromElem
vec::SpecFromElem provides an optimization to use calloc to fill a Vec
when the element given to fill the Vec is represented by 0.
For floats, the test for that currently used is `x == 0. &&
x.is_sign_positive()`. When compiled in a standalone function, rustc
generates the following assembly:
```
xorps xmm1, xmm1
ucomisd xmm0, xmm1
setnp al
sete cl
and cl, al
movq rax, xmm0
test rax, rax
setns al
and al, cl
ret
```
A simpler test telling us whether the value is represented by 0, is
`x.to_bits() == 0`, which rustc compiles to:
```
movq rax, xmm0
test rax, rax
sete al
ret
```
Not that the test is hot in any way, but it also makes it clearer what
the intent in the rust code is.
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This is the `Alloc` trait and its dependencies.
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These unstable items are deprecated:
* The `std::collections::range::RangeArgument` reexport
* The `std::collections::range` module.
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The stable reexport `std::collections::Bound` is now deprecated.
Another deprecated reexport could be added in `alloc`,
but that crate is unstable.
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It' only used for hash::Hasher, but Hasher is also imported.
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vec::SpecFromElem provides an optimization to use calloc to fill a Vec
when the element given to fill the Vec is represented by 0.
For floats, the test for that currently used is `x == 0. &&
x.is_sign_positive()`. When compiled in a standalone function, rustc
generates the following assembly:
```
xorps xmm1, xmm1
ucomisd xmm0, xmm1
setnp al
sete cl
and cl, al
movq rax, xmm0
test rax, rax
setns al
and al, cl
ret
```
A simpler test telling us whether the value is represented by 0, is
`x.to_bits() == 0`, which rustc compiles to:
```
movq rax, xmm0
test rax, rax
sete al
ret
```
Not that the test is hot in any way, but it also makes it clearer what
the intent in the rust code is.
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Clarify "length" wording in `Vec::with_capacity`.
Fixes https://github.com/rust-lang/rust/issues/49448.
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Implement `shrink_to` method on collections
Fixes #49385
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Stabilize method `String::retain`
Closes #43874
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Add missing '?' to format grammar.
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Add is_whitespace and is_alphanumeric to str.
The other methods from `UnicodeStr` are already stable inherent
methods on str, but these have not been included.
r? @SimonSapin
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Add slice::sort_by_cached_key as a memoised sort_by_key
At present, `slice::sort_by_key` calls its key function twice for each comparison that is made. When the key function is expensive (which can often be the case when `sort_by_key` is chosen over `sort_by`), this can lead to very suboptimal behaviour.
To address this, I've introduced a new slice method, `sort_by_cached_key`, which has identical semantic behaviour to `sort_by_key`, except that it guarantees the key function will only be called once per element.
Where there are `n` elements and the key function is `O(m)`:
- `slice::sort_by_cached_key` time complexity is `O(m n log m n)`, compared to `slice::sort_by_key`'s `O(m n + n log n)`.
- `slice::sort_by_cached_key` space complexity remains at `O(n + m)`. (Technically, it now reserves a slice of size `n`, whereas before it reserved a slice of size `n/2`.)
`slice::sort_unstable_by_key` has not been given an analogue, as it is important that unstable sorts are in-place, which is not a property that is guaranteed here. However, this also means that `slice::sort_unstable_by_key` is likely to be slower than `slice::sort_by_cached_key` when the key function does not have negligible complexity. We might want to explore this trade-off further in the future.
Benchmarks (for a vector of 100 `i32`s):
```
# Lexicographic: `|x| x.to_string()`
test bench_sort_by_key ... bench: 112,638 ns/iter (+/- 19,563)
test bench_sort_by_cached_key ... bench: 15,038 ns/iter (+/- 4,814)
# Identity: `|x| *x`
test bench_sort_by_key ... bench: 1,346 ns/iter (+/- 238)
test bench_sort_by_cached_key ... bench: 1,839 ns/iter (+/- 765)
# Power: `|x| x.pow(31)`
test bench_sort_by_key ... bench: 3,624 ns/iter (+/- 738)
test bench_sort_by_cached_key ... bench: 1,997 ns/iter (+/- 311)
# Abs: `|x| x.abs()`
test bench_sort_by_key ... bench: 1,546 ns/iter (+/- 174)
test bench_sort_by_cached_key ... bench: 1,668 ns/iter (+/- 790)
```
(So it seems functions that are single operations do perform slightly worse with this method, but for pretty much any more complex key, you're better off with this optimisation.)
I've definitely found myself using expensive keys in the past and wishing this optimisation was made (e.g. for https://github.com/rust-lang/rust/pull/47415). This feels like both desirable and expected behaviour, at the small cost of slightly more stack allocation and minute degradation in performance for extremely trivial keys.
Resolves #34447.
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Stabilize 128-bit integers :tada:
cc #35118
EDIT: This should be merged only after the following have been merged:
- [x] https://github.com/rust-lang-nursery/compiler-builtins/pull/236
- [x] https://github.com/rust-lang/book/pull/1230
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The other methods from `UnicodeStr` are already stable inherent
methods on str, but these have not been included.
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Make resuming generators unsafe instead of the creation of immovable generators
cc @withoutboats
Fixes #47787
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Stabilise FromUtf8Error::as_bytes
Closes #40895.
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Add 12 num::NonZero* types for primitive integers, deprecate core::nonzero
RFC: https://github.com/rust-lang/rfcs/pull/2307
Tracking issue: ~~https://github.com/rust-lang/rust/issues/27730~~ https://github.com/rust-lang/rust/issues/49137
Fixes https://github.com/rust-lang/rust/issues/27730
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address some FIXME whose associated issues were marked as closed
part of #44366
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generators. Fixes #47787
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Rollup of 17 pull requests
- Successful merges: #46518, #48810, #48834, #48902, #49004, #49092, #49096, #49099, #49104, #49125, #49139, #49152, #49157, #49161, #49166, #49176, #49184
- Failed merges:
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Stabilize slice patterns without `..`
And merge `feature(advanced_slice_patterns)` into `feature(slice_patterns)`.
The detailed description can be found in https://github.com/rust-lang/rust/issues/48836.
Slice patterns were unstable for long time since before 1.0 due to many bugs in the implementation, now this stabilization is possible primarily due to work of @arielb1 who [wrote the new MIR-based implementation of slice patterns](https://github.com/rust-lang/rust/pull/32202) and @mikhail-m1 who [fixed one remaining class of codegen issues](https://github.com/rust-lang/rust/pull/47926).
Reference PR https://github.com/rust-lang-nursery/reference/pull/259
cc https://github.com/rust-lang/rust/issues/23121
fixes #48836
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Merge `feature(advanced_slice_patterns)` into `feature(slice_patterns)`
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Pin, Unpin, PinBox
Implementing rust-lang/rfcs#2349 (do not merge until RFC is merged)
@bors r? @cramertj
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Add hexadecimal formatting of integers with fmt::Debug
This can be used for integers within a larger types which implements Debug (possibly through derive) but not fmt::UpperHex or fmt::LowerHex.
```rust
assert!(format!("{:02x?}", b"Foo\0") == "[46, 6f, 6f, 00]");
assert!(format!("{:02X?}", b"Foo\0") == "[46, 6F, 6F, 00]");
```
RFC: https://github.com/rust-lang/rfcs/pull/2226
The new formatting string syntax (`x?` and `X?`) is insta-stable in this PR because I don’t know how to change a built-in proc macro’s behavior based of a feature gate. I can look into adding that, but I also strongly suspect that keeping this feature unstable for a time period would not be useful as possibly no-one would use it during that time.
This PR does not add the new (public) `fmt::Formatter` proposed in the API because:
* There was some skepticism on response to this part of the RFC
* It is not possible to implement as-is without larger changes to `fmt`, because `Formatter` at the moment has no easy way to tell apart for example `Octal` from `Binary`: it only has a function pointer for the relevant `fmt()` method.
If some integer-like type outside of `std` want to implement this behavior, another RFC will likely need to propose a different public API for `Formatter`.
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Closes #40895.
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