@jongiddy noticed bad performance due to the lack of inlining on `then`
and `then_with`. I confirmed that inlining really is the culprit by
creating a custom `then` function and repeating his benchmark on my
machine with and without the `#[inline]` attribute.
The numbers were exactly the same on my machine without the attribute.
With `#[inline]` I got the same performance as I did with manually
inlined implementation.
Their relationship is:
* `resume_from = error_len.map(|l| l + valid_up_to)`
* error_len is always one of None, Some(1), Some(2), or Some(3).
When I started using resume_from I almost always ended up subtracting
valid_up_to to obtain error_len.
Therefore the latter is what should be provided in the first place.
Primarily opened to address the concerns brought up in
https://github.com/rust-lang/rust/issues/40498.
* run rustfmt on code blocks
* use `DefaultHasher` instead of deprecated `SipHasher`
* rename `hash` to `calculate_hash` to prevent confusion with the `hash`
method
This reverts commit 7f1d1c6d9a.
The original commit was created because mdBook and rustdoc had
different generation algorithms for header links; now with
https://github.com/rust-lang/rust/pull/39966 , the algorithms
are the same. So let's undo this change.
... when I came across this problem, I said "eh, this isn't fun,
but it doesn't take that long." I probably should have just actually
taken the time to fix upstream, given that they were amenable. Oh
well!
Allow more Cell methods for non-Copy types
Clearly, `get_mut` is safe for any `T`. The other two only provide unsafe pointers anyway.
The only remaining inherent method with `Copy` bound is `get`, which sounds about right to me.
I found the order if `impl` blocks in the file a little weird (first inherent impl, then some trait impls, then another inherent impl), but didn't change it to keep the diff small.
Contributes to #39264
Port books to mdbook
Part of https://github.com/rust-lang/rust/issues/39588
blocked on https://github.com/rust-lang/rust/pull/39431
As a first step towards the bookshelf, we ~vendor mdbook in-tree and~ port our books to it. Eventually, both of these books will be moved out-of-tree, but the nightly book will rely on doing the same thing. As such, this intermediate step is useful.
r? @alexcrichton @brson
/cc @azerupi
Add PartialOrd, Ord derivations to TypeId
I want to be able to sort a `Vec` of types which contain `TypeId`s, so an `Ord` derivation would be very useful to me. `Hash` and `PartialEq`/`Eq` already exist, so the missing `PartialOrd` and `Ord` derivations feel like an oversight to me.
improve error message when two-arg assert_eq! receives a trailing comma
Previously, `assert_eq!(left, right,)` (respectively, `assert_ne!(left,
right,)`; note the trailing comma) would result in a confusing "requires
at least a format string argument" error. In reality, a format string is
optional, but the trailing comma puts us into the "match a token tree of
zero or more tokens" branch of the macro (in order to support the
optional format string), and passing the empty token tree into
`format_args!` results in the confusing error. If instead we match a
token tree of one or more tokens, we get a much more sensible
"unexpected end of macro invocation" error.
While we're here, fix up a stray space before a comma in the match
guards.
Resolves#39369.
-----
**Before:**
```
$ rustc scratch.rs
error: requires at least a format string argument
--> scratch.rs:2:5
|
2 | assert_eq!(1, 2,);
| ^^^^^^^^^^^^^^^^^^
|
= note: this error originates in a macro outside of the current crate
error: aborting due to previous error
```
**After:**
```
$ ./build/x86_64-unknown-linux-gnu/stage1/bin/rustc scratch.rs
error: unexpected end of macro invocation
--> scratch.rs:2:20
|
2 | assert_eq!(1, 2,);
| ^
```
Fix a misleading statement in `Iterator.nth()`
The `Iterator.nth()` documentation says "Note that all preceding elements will be consumed". I assumed from that that the preceding elements would be the *only* ones that were consumed, but in fact the returned element is consumed as well.
The way I read the documentation, I assumed that `nth(0)` would not discard anything (there are 0 preceding elements, and maybe it just peeks at the start of the iterator somehow), so I added a sentence clarifying that it does. I also rephrased it to avoid the stunted "i.e." phrasing.
Specialize `PartialOrd<A> for [A] where A: Ord`
This way we can call `cmp` instead of `partial_cmp` in the loop, removing some burden of optimizing `Option`s away from the compiler.
PR #39538 introduced a regression where sorting slices suddenly became slower, since `slice1.lt(slice2)` was much slower than `slice1.cmp(slice2) == Less`. This problem is now fixed.
To verify, I benchmarked this simple program:
```rust
fn main() {
let mut v = (0..2_000_000).map(|x| x * x * x * 18913515181).map(|x| vec![x, x ^ 3137831591]).collect::<Vec<_>>();
v.sort();
}
```
Before this PR, it would take 0.95 sec, and now it takes 0.58 sec.
I also tried changing the `is_less` lambda to use `cmp` and `partial_cmp`. Now all three versions (`lt`, `cmp`, `partial_cmp`) are equally performant for sorting slices - all of them take 0.58 sec on the
benchmark.
Tangentially, as soon as we get `default impl`, it might be a good idea to implement a blanket default impl for `lt`, `gt`, `le`, `ge` in terms of `cmp` whenever possible. Today, those four functions by default are only implemented in terms of `partial_cmp`.
r? @alexcrichton
The `Iterator.nth()` documentation says "Note that all preceding elements will be consumed". I assumed from that that the preceding elements would be the *only* ones that were consumed, but in fact the returned element is consumed as well.
The way I read the documentation, I assumed that `nth(0)` would not discard anything (as there are 0 preceding elements), so I added a sentence clarifying that it does. I also rephrased it to avoid the stunted "i.e." phrasing.
Improve format float
* Move float into mod float like in test
* Add more tests for f64 f32, lower exp, upper exp, which can come if handy in the future if we want refactor further
* Use `assert_eq` for clearer error messages
