Use stable code in doc examples (libcollections)
Main task is to change from String::from_str to String::from in examples for String
(the latter constructor is stable). While I'm at it, also remove redundant feature flags,
fix some other instances of unstable code in examples (in examples for stable
methods), and remove some use of usize in examples too.
Prefer String::from over from_str; String::from_str is unstable while
String::from is stable. Promote the latter by using it in examples.
Simply migrating unstable function to the closest alternative.
Some modest running-time improvements to `std::collections::BitSet` on bit-sets of varying set-membership densities. This is work originally from [here](https://github.com/rayglover/alt_collections). (Benchmarks copied below)
```
std::collections::BitSet / alt_collections::BitSet
copy_dense ... 3.08x
copy_sparse ... 4.22x
count_dense ... 11.01x
count_sparse ... 8.11x
from_bytes ... 1.47x
intersect_dense ... 6.54x
intersect_sparse ... 4.37x
union_dense ... 5.53x
union_sparse ... 5.60x
```
The exception is `from_bytes`, which I've left unaltered since the optimization is rather obscure.
Compiling with the cpu feature `popcnt` gave a further ~10% improvement on my machine, but this wasn't factored in to the benchmarks above.
Similar improvements could be made to `BitVec`, although that would probably require more substantial changes.
criticism welcome!
Using regular pointer arithmetic to iterate collections of zero-sized types
doesn't work, because we'd get the same pointer all the time. Our
current solution is to convert the pointer to an integer, add an offset
and then convert back, but this inhibits certain optimizations.
What we should do instead is to convert the pointer to one that points
to an i8\*, and then use a LLVM GEP instructions without the inbounds
flag to perform the pointer arithmetic. This allows to generate pointers
that point outside allocated objects without causing UB (as long as you
don't dereference them), and it wraps around using two's complement,
i.e. it behaves exactly like the wrapping_* operations we're currently
using, with the added benefit of LLVM being able to better optimize the
resulting IR.
Using regular pointer arithmetic to iterate collections of zero-sized types
doesn't work, because we'd get the same pointer all the time. Our
current solution is to convert the pointer to an integer, add an offset
and then convert back, but this inhibits certain optimizations.
What we should do instead is to convert the pointer to one that points
to an i8*, and then use a LLVM GEP instructions without the inbounds
flag to perform the pointer arithmetic. This allows to generate pointers
that point outside allocated objects without causing UB (as long as you
don't dereference them), and it wraps around using two's complement,
i.e. it behaves exactly like the wrapping_* operations we're currently
using, with the added benefit of LLVM being able to better optimize the
resulting IR.
The functions BitSet::{iter,union,symmetric_difference} each had docs that claimed u32s were output when their actual output each end up being usizes.
r? @steveklabnik
We don't need to copy any elements if `at` is behind the last element
in the map. The last element is at index `self.v.len() - 1`, so we
should not copy if `at` is greater **or equals** `self.v.len()`.
r? @Gankro
Several Minor API / Reference Documentation Fixes
- Fix a few small errors in the reference.
- Fix paper cuts in the API docs.
Fixes#24882Fixes#25233Fixes#25250
We don't need to copy any elements if `at` is behind the last element
in the map. The last element is at index `self.v.len() - 1`, so we
should not copy if `at` is greater or equals `self.v.len()`.
I was profiling my code again and this time AsRef<str> for String
was eating up a considerable chunk of my runtime; adding the inline
annotation made the program run almost twice as fast!
While I was at it I also added the annotation to other implementations
of AsRef as well as AsMut.
Ideally this trait implementation would be unstable, requiring crates to opt-in
if they would like the functionality, but that's not currently how stability
works so the implementation needs to be removed entirely.
This may come back at a future date, but for now the conservative option is to
remove it.
[breaking-change]
Ideally this trait implementation would be unstable, requiring crates to opt-in
if they would like the functionality, but that's not currently how stability
works so the implementation needs to be removed entirely.
This may come back at a future date, but for now the conservative option is to
remove it.
[breaking-change]
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).
