collections: Convert SliceConcatExt to use associated types
Coherence now allows this, we have `SliceConcatExt<T> for [V] where T: Sized + Clone` and` SliceConcatExt<str> for [S]`, these don't conflict because
str is never Sized.
According to rust-lang/rfcs#235, `VecDeque` should have this method (`VecDeque` was called `RingBuf` at the time) but it was never implemented.
I marked this stable since "1.0.0" because it's stable in `Vec`.
Coherence now allows this, we have SliceConcatExt<T> for [V] where T: Sized
+ Clone and SliceConcatExt<str> for [S], these don't conflict because
str is never Sized.
This commit does two things: it adds an example for indexing vectors, and it changes the \"Examples\" section to use full sentences.
This change was spurred by someone in the #rust IRC channel asking if there was a `.set()` method for changing the `i`-th value of a vector (they had missed that `Vec` implements `IndexMut`, which is easy to do if you're not aware of that trait).
This makes the `bit::vec::bench::bench_bit_vec_big_union` benchmark go
from `774 ns/iter (+/- 190)` to `602 ns/iter (+/- 5)`.
(There's room for more work here too: if one can guarantee 128-bit
alignment for the vector, the compiler actually optimises `union`,
`intersection` etc. to SIMD instructions, which end up being ~5x faster
that the original version, and 4x faster than the optimised version in
this patch.)
This makes the `bit::vec::bench::bench_bit_vec_big_union` benchmark go
from `774 ns/iter (+/- 190)` to `602 ns/iter (+/- 5)`.
(There's room for more work here too: if one can guarantee 128-bit
alignment for the vector, the compiler actually optimises `union`,
`intersection` etc. to SIMD instructions, which end up being ~5x faster
that the original version, and 4x faster than the optimised version in
this patch.)
collections: Implement String::drain(range) according to RFC 574
`.drain(range)` is unstable and under feature(collections_drain).
This adds a safe way to remove any range of a String as efficiently as
possible.
As noted in the code, this drain iterator has none of the memory safety
issues of the vector version.
RFC tracking issue is #23055
These implementations were intended to be unstable, but currently the stability
attributes cannot handle a stable trait with an unstable `impl` block. This
commit also audits the rest of the standard library for explicitly-`#[unstable]`
impl blocks. No others were removed but some annotations were changed to
`#[stable]` as they're defacto stable anyway.
One particularly interesting `impl` marked `#[stable]` as part of this commit
is the `Add<&[T]>` impl for `Vec<T>`, which uses `push_all` and implicitly
clones all elements of the vector provided.
Closes#24791
[breaking-change]
`.drain(range)` is unstable and under feature(collections_drain).
This adds a safe way to remove any range of a String as efficiently as
possible.
As noted in the code, this drain iterator has none of the memory safety
issues of the vector version.
RFC tracking issue is #23055
These implementations were intended to be unstable, but currently the stability
attributes cannot handle a stable trait with an unstable `impl` block. This
commit also audits the rest of the standard library for explicitly-`#[unstable]`
impl blocks. No others were removed but some annotations were changed to
`#[stable]` as they're defacto stable anyway.
One particularly interesting `impl` marked `#[stable]` as part of this commit
is the `Add<&[T]>` impl for `Vec<T>`, which uses `push_all` and implicitly
clones all elements of the vector provided.
Closes#24791
Implement Vec::drain(\<range type\>) from rust-lang/rfcs#574, tracking issue #23055.
This is a big step forward for vector usability. This is an introduction of an API for removing a range of *m* consecutive elements from a vector, as efficently as possible.
New features:
- Introduce trait `std::collections::range::RangeArgument` implemented by all four built-in range types.
- Change `Vec::drain()` to use `Vec::drain<R: RangeArgument>(R)`
Implementation notes:
- Use @Gankro's idea for memory safety: Use `set_len` on the source vector when creating the iterator, to make sure that the part of the vector that will be modified is unreachable. Fix up things in Drain's destructor — but even if it doesn't run, we don't expose any moved-out-from slots of the vector.
- This `.drain<R>(R)` very close to how it is specified in the RFC.
- Introduced as unstable
- Drain reuses the slice iterator — copying and pasting the same iterator pointer arithmetic again felt very bad
- The `usize` index as a range argument in the RFC is not included. The ranges trait would have to change to accomodate it.
Please help me with:
- Name and location of the new ranges trait.
- Design of the ranges trait
- Understanding Niko's comments about variance (Note: for a long time I was using a straight up &mut Vec in the iterator, but I changed this to permit reusing the slice iterator).
Previous PR and discussion: #23071
Improve example for as_string and add example for as_vec
Provide a better example of `as_string` / `DerefString`'s unique capabilities.
Use an example where (for an unspecified reason) you need a &String, and
show how `as_string` solves the problem without needing an allocation.
Changes the style guidelines regarding unit tests to recommend using a
sub-module named "tests" instead of "test" for unit tests as "test"
might clash with imports of libtest.
This is an implementation of [RFC 1030][rfc] which adds these traits to the
prelude and additionally removes all inherent `into_iter` methods on collections
in favor of the trait implementation (which is now accessible by default).
[rfc]: https://github.com/rust-lang/rfcs/pull/1030
This is technically a breaking change due to the prelude additions and removal
of inherent methods, but it is expected that essentially no code breaks in
practice.
[breaking-change]
Closes#24538
as accepted in [RFC 526](https://github.com/rust-lang/rfcs/blob/master/text/0526-fmt-text-writer.md).
Note that this brand new method is marked as **stable**. I judged this safe enough: it’s simple enough that it’s very unlikely to change. Still, I can mark it unstable instead if you prefer.
r? @alexcrichton
For now, words() is left in (but deprecated), and Words is a type alias for
struct SplitWhitespace.
Also cleaned up references to s.words() throughout codebase.
Closes#15628
This commit removes all the old casting/generic traits from `std::num` that are
no longer in use by the standard library. This additionally removes the old
`strconv` module which has not seen much use in quite a long time. All generic
functionality has been supplanted with traits in the `num` crate and the
`strconv` module is supplanted with the [rust-strconv crate][rust-strconv].
[rust-strconv]: https://github.com/lifthrasiir/rust-strconv
This is a breaking change due to the removal of these deprecated crates, and the
alternative crates are listed above.
[breaking-change]
