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Make more primitive integer methods const
Now that #72437 has been merged and `const_if_match` is stable, these methods can be stabilized const. The methods are grouped in commits according to feature names:
* `const_nonzero_int_methods`
- `NonZero*::new`
* some `const_checked_int_methods`
- `{i*,u*}::checked_add`
- `{i*,u*}::checked_sub`
- `{i*,u*}::checked_mul`
- `{i*,u*}::checked_neg`
- `{i*,u*}::checked_shl`
- `{i*,u*}::checked_shr`
- `i*::checked_abs`
* `const_saturating_int_methods`
- `{i*,u*}::saturating_add`
- `{i*,u*}::saturating_sub`
- `{i*,u*}::saturating_mul`
- `i*::saturating_neg`
- `i*::saturating_abs`
* `const_int_sign`
- `i*::signum`
* `const_ascii_ctype_on_intrinsics`
- `{char,u8}::is_ascii_alphabetic`
- `{char,u8}::is_ascii_uppercase`
- `{char,u8}::is_ascii_lowercase`
- `{char,u8}::is_ascii_alphanumeric`
- `{char,u8}::is_ascii_digit`
- `{char,u8}::is_ascii_hexdigit`
- `{char,u8}::is_ascii_punctuation`
- `{char,u8}::is_ascii_graphic`
- `{char,u8}::is_ascii_whitespace`
- `{char,u8}::is_ascii_control`
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Rearrange the pipeline of `pow` to gain efficiency
The check of the `exp` parameter seems useless if we execute the while-loop more than once.
The original implementation of `pow` function using one more comparison if the `exp==0` and may break the pipeline of the cpu, which may generate a slower code.
The performance gap between the old and the new implementation may be small, but IMO, at least the newer one looks more beautiful.
---
bench prog:
```
#![feature(test)]
extern crate test;
#[macro_export]macro_rules! timing{
($a:expr)=>{let time=std::time::Instant::now();{$a;}print!("{:?} ",time.elapsed())};
($a:expr,$b:literal)=>{let time=std::time::Instant::now();let mut a=0;for _ in 0..$b{a^=$a;}print!("{:?} {} ",time.elapsed(),a)}
}
#[inline]
pub fn pow_rust(x:i64, mut exp: u32) -> i64 {
let mut base = x;
let mut acc = 1;
while exp > 1 {
if (exp & 1) == 1 {
acc = acc * base;
}
exp /= 2;
base = base * base;
}
if exp == 1 {
acc = acc * base;
}
acc
}
#[inline]
pub fn pow_new(x:i64, mut exp: u32) -> i64 {
if exp==0{
1
}else{
let mut base = x;
let mut acc = 1;
while exp > 1 {
if (exp & 1) == 1 {
acc = acc * base;
}
exp >>= 1;
base = base * base;
}
acc * base
}
}
fn main(){
let a=2i64;
let b=1_u32;
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
}
```
bench in my laptop:
```
neutron@Neutron:/me/rust$ rc commit.rs
rustc commit.rs && ./commit
3.978419716s 0 4.079765171s 0 3.964630622s 0
3.997127013s 0 4.260304804s 0 3.997638211s 0
3.963195544s 0 4.11657718s 0 4.176054164s 0
3.830128579s 0 3.980396122s 0 3.937258567s 0
3.986055948s 0 4.127804162s 0 4.018943411s 0
4.185568857s 0 4.217512517s 0 3.98313603s 0
3.863018225s 0 4.030447988s 0 3.694878237s 0
4.206987927s 0 4.137608047s 0 4.115564664s 0
neutron@Neutron:/me/rust$ rc commit.rs -O
rustc commit.rs -O && ./commit
162.111993ms 0 165.107125ms 0 166.26924ms 0
175.20479ms 0 205.062565ms 0 176.278791ms 0
174.408975ms 0 166.526899ms 0 201.857604ms 0
146.190062ms 0 168.592821ms 0 154.61411ms 0
199.678912ms 0 168.411598ms 0 162.129996ms 0
147.420765ms 0 209.759326ms 0 154.807907ms 0
165.507134ms 0 188.476239ms 0 157.351524ms 0
121.320123ms 0 126.401229ms 0 114.86428ms 0
```
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libstd/libcore: fix various typos
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The check of the `exp` parameter seems useless if we execute the while-loop more than once.
The original implementation of `pow` function using one more comparison if the `exp==0` and may break the pipeline of the cpu, which may generate a slower code.
The performance gap between the old and the new implementation may be small, but IMO, at least the newer one looks more beautiful.
---
bench prog:
```
extern crate test;
($a:expr)=>{let time=std::time::Instant::now();{$a;}print!("{:?} ",time.elapsed())};
($a:expr,$b:literal)=>{let time=std::time::Instant::now();let mut a=0;for _ in 0..$b{a^=$a;}print!("{:?} {} ",time.elapsed(),a)}
}
pub fn pow_rust(x:i64, mut exp: u32) -> i64 {
let mut base = x;
let mut acc = 1;
while exp > 1 {
if (exp & 1) == 1 {
acc = acc * base;
}
exp /= 2;
base = base * base;
}
if exp == 1 {
acc = acc * base;
}
acc
}
pub fn pow_new(x:i64, mut exp: u32) -> i64 {
if exp==0{
1
}else{
let mut base = x;
let mut acc = 1;
while exp > 1 {
if (exp & 1) == 1 {
acc = acc * base;
}
exp >>= 1;
base = base * base;
}
acc * base
}
}
fn main(){
let a=2i64;
let b=1_u32;
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
timing!(test::black_box(a).pow(test::black_box(b)),100000000);
timing!(pow_new(test::black_box(a),test::black_box(b)),100000000);
timing!(pow_rust(test::black_box(a),test::black_box(b)),100000000);
println!();
}
```
bench in my laptop:
```
neutron@Neutron:/me/rust$ rc commit.rs
rustc commit.rs && ./commit
3.978419716s 0 4.079765171s 0 3.964630622s 0
3.997127013s 0 4.260304804s 0 3.997638211s 0
3.963195544s 0 4.11657718s 0 4.176054164s 0
3.830128579s 0 3.980396122s 0 3.937258567s 0
3.986055948s 0 4.127804162s 0 4.018943411s 0
4.185568857s 0 4.217512517s 0 3.98313603s 0
3.863018225s 0 4.030447988s 0 3.694878237s 0
4.206987927s 0 4.137608047s 0 4.115564664s 0
neutron@Neutron:/me/rust$ rc commit.rs -O
rustc commit.rs -O && ./commit
162.111993ms 0 165.107125ms 0 166.26924ms 0
175.20479ms 0 205.062565ms 0 176.278791ms 0
174.408975ms 0 166.526899ms 0 201.857604ms 0
146.190062ms 0 168.592821ms 0 154.61411ms 0
199.678912ms 0 168.411598ms 0 162.129996ms 0
147.420765ms 0 209.759326ms 0 154.807907ms 0
165.507134ms 0 188.476239ms 0 157.351524ms 0
121.320123ms 0 126.401229ms 0 114.86428ms 0
```
delete an unnecessary semicolon...
Sorry for the typo.
delete trailing whitespace
Sorry, too..
Sorry for the missing...
I checked all the implementations, and finally found that there is one function that does not check whether `exp == 0`
add extra tests
add extra tests.
finished adding the extra tests to prevent further typo
add pow(2) to negative exp
add whitespace.
add whitespace
add whitespace
delete extra line
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Closes #66770.
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Optimise fast path of checked_ops with `unlikely`
This PR marks paths returning `None` in checked_ops as unlikely to improvde codegen.
Fixes #73731
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And final part!!!
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stabilize leading_trailing_ones
This PR stabilizes the `leading_trailing_ones` feature. It's been available on nightly since the start of the year, and hasn't had any issues since. It seems unlikely we'll want to change this, so following up on @djc's suggestion in https://github.com/rust-lang/rust/issues/57969#issuecomment-638405264 I'd like to put forward this PR to stabilize the feature and make it part of `1.46.0`. Thanks!
cc/ @djc @rust-lang/libs
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Migrate to numeric associated consts
The deprecation PR is #72885
cc #68490
cc rust-lang/rfcs#2700
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Co-authored-by: lzutao <taolzu@gmail.com>
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`saturating_add` example was not parameterized, but passed because the `u8` would saturate successfully
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Co-authored-by: bluss <bluss@users.noreply.github.com>
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Co-authored-by: bluss <bluss@users.noreply.github.com>
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Stabilize saturating_abs and saturating_neg
Stabilizes the following signed integer functions with saturation mechanics:
* saturating_abs()
* saturating_neg()
Closes #59983
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doc: add links to rotate_(left|right)
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Rework the std::iter::Step trait
Previous attempts: #43127 #62886 #68807
Tracking issue: #42168
This PR reworks the `Step` trait to be phrased in terms of the *successor* and *predecessor* operations. With this, `Step` hopefully has a consistent identity that can have a path towards stabilization. The proposed trait:
```rust
/// Objects that have a notion of *successor* and *predecessor* operations.
///
/// The *successor* operation moves towards values that compare greater.
/// The *predecessor* operation moves towards values that compare lesser.
///
/// # Safety
///
/// This trait is `unsafe` because its implementation must be correct for
/// the safety of `unsafe trait TrustedLen` implementations, and the results
/// of using this trait can otherwise be trusted by `unsafe` code to be correct
/// and fulful the listed obligations.
pub unsafe trait Step: Clone + PartialOrd + Sized {
/// Returns the number of *successor* steps required to get from `start` to `end`.
///
/// Returns `None` if the number of steps would overflow `usize`
/// (or is infinite, or if `end` would never be reached).
///
/// # Invariants
///
/// For any `a`, `b`, and `n`:
///
/// * `steps_between(&a, &b) == Some(n)` if and only if `Step::forward(&a, n) == Some(b)`
/// * `steps_between(&a, &b) == Some(n)` if and only if `Step::backward(&a, n) == Some(a)`
/// * `steps_between(&a, &b) == Some(n)` only if `a <= b`
/// * Corollary: `steps_between(&a, &b) == Some(0)` if and only if `a == b`
/// * Note that `a <= b` does _not_ imply `steps_between(&a, &b) != None`;
/// this is the case wheen it would require more than `usize::MAX` steps to get to `b`
/// * `steps_between(&a, &b) == None` if `a > b`
fn steps_between(start: &Self, end: &Self) -> Option<usize>;
/// Returns the value that would be obtained by taking the *successor*
/// of `self` `count` times.
///
/// If this would overflow the range of values supported by `Self`, returns `None`.
///
/// # Invariants
///
/// For any `a`, `n`, and `m`:
///
/// * `Step::forward_checked(a, n).and_then(|x| Step::forward_checked(x, m)) == Step::forward_checked(a, m).and_then(|x| Step::forward_checked(x, n))`
///
/// For any `a`, `n`, and `m` where `n + m` does not overflow:
///
/// * `Step::forward_checked(a, n).and_then(|x| Step::forward_checked(x, m)) == Step::forward_checked(a, n + m)`
///
/// For any `a` and `n`:
///
/// * `Step::forward_checked(a, n) == (0..n).try_fold(a, |x, _| Step::forward_checked(&x, 1))`
/// * Corollary: `Step::forward_checked(&a, 0) == Some(a)`
fn forward_checked(start: Self, count: usize) -> Option<Self>;
/// Returns the value that would be obtained by taking the *successor*
/// of `self` `count` times.
///
/// If this would overflow the range of values supported by `Self`,
/// this function is allowed to panic, wrap, or saturate.
/// The suggested behavior is to panic when debug assertions are enabled,
/// and to wrap or saturate otherwise.
///
/// Unsafe code should not rely on the correctness of behavior after overflow.
///
/// # Invariants
///
/// For any `a`, `n`, and `m`, where no overflow occurs:
///
/// * `Step::forward(Step::forward(a, n), m) == Step::forward(a, n + m)`
///
/// For any `a` and `n`, where no overflow occurs:
///
/// * `Step::forward_checked(a, n) == Some(Step::forward(a, n))`
/// * `Step::forward(a, n) == (0..n).fold(a, |x, _| Step::forward(x, 1))`
/// * Corollary: `Step::forward(a, 0) == a`
/// * `Step::forward(a, n) >= a`
/// * `Step::backward(Step::forward(a, n), n) == a`
fn forward(start: Self, count: usize) -> Self {
Step::forward_checked(start, count).expect("overflow in `Step::forward`")
}
/// Returns the value that would be obtained by taking the *successor*
/// of `self` `count` times.
///
/// # Safety
///
/// It is undefined behavior for this operation to overflow the
/// range of values supported by `Self`. If you cannot guarantee that this
/// will not overflow, use `forward` or `forward_checked` instead.
///
/// # Invariants
///
/// For any `a`:
///
/// * if there exists `b` such that `b > a`, it is safe to call `Step::forward_unchecked(a, 1)`
/// * if there exists `b`, `n` such that `steps_between(&a, &b) == Some(n)`,
/// it is safe to call `Step::forward_unchecked(a, m)` for any `m <= n`.
///
/// For any `a` and `n`, where no overflow occurs:
///
/// * `Step::forward_unchecked(a, n)` is equivalent to `Step::forward(a, n)`
#[unstable(feature = "unchecked_math", reason = "niche optimization path", issue = "none")]
unsafe fn forward_unchecked(start: Self, count: usize) -> Self {
Step::forward(start, count)
}
/// Returns the value that would be obtained by taking the *successor*
/// of `self` `count` times.
///
/// If this would overflow the range of values supported by `Self`, returns `None`.
///
/// # Invariants
///
/// For any `a`, `n`, and `m`:
///
/// * `Step::backward_checked(a, n).and_then(|x| Step::backward_checked(x, m)) == n.checked_add(m).and_then(|x| Step::backward_checked(a, x))`
/// * `Step::backward_checked(a, n).and_then(|x| Step::backward_checked(x, m)) == try { Step::backward_checked(a, n.checked_add(m)?) }`
///
/// For any `a` and `n`:
///
/// * `Step::backward_checked(a, n) == (0..n).try_fold(a, |x, _| Step::backward_checked(&x, 1))`
/// * Corollary: `Step::backward_checked(&a, 0) == Some(a)`
fn backward_checked(start: Self, count: usize) -> Option<Self>;
/// Returns the value that would be obtained by taking the *predecessor*
/// of `self` `count` times.
///
/// If this would overflow the range of values supported by `Self`,
/// this function is allowed to panic, wrap, or saturate.
/// The suggested behavior is to panic when debug assertions are enabled,
/// and to wrap or saturate otherwise.
///
/// Unsafe code should not rely on the correctness of behavior after overflow.
///
/// # Invariants
///
/// For any `a`, `n`, and `m`, where no overflow occurs:
///
/// * `Step::backward(Step::backward(a, n), m) == Step::backward(a, n + m)`
///
/// For any `a` and `n`, where no overflow occurs:
///
/// * `Step::backward_checked(a, n) == Some(Step::backward(a, n))`
/// * `Step::backward(a, n) == (0..n).fold(a, |x, _| Step::backward(x, 1))`
/// * Corollary: `Step::backward(a, 0) == a`
/// * `Step::backward(a, n) <= a`
/// * `Step::forward(Step::backward(a, n), n) == a`
fn backward(start: Self, count: usize) -> Self {
Step::backward_checked(start, count).expect("overflow in `Step::backward`")
}
/// Returns the value that would be obtained by taking the *predecessor*
/// of `self` `count` times.
///
/// # Safety
///
/// It is undefined behavior for this operation to overflow the
/// range of values supported by `Self`. If you cannot guarantee that this
/// will not overflow, use `backward` or `backward_checked` instead.
///
/// # Invariants
///
/// For any `a`:
///
/// * if there exists `b` such that `b < a`, it is safe to call `Step::backward_unchecked(a, 1)`
/// * if there exists `b`, `n` such that `steps_between(&b, &a) == Some(n)`,
/// it is safe to call `Step::backward_unchecked(a, m)` for any `m <= n`.
///
/// For any `a` and `n`, where no overflow occurs:
///
/// * `Step::backward_unchecked(a, n)` is equivalent to `Step::backward(a, n)`
#[unstable(feature = "unchecked_math", reason = "niche optimization path", issue = "none")]
unsafe fn backward_unchecked(start: Self, count: usize) -> Self {
Step::backward(start, count)
}
}
```
Note that all of these are associated functions and not callable via method syntax; the calling syntax is always `Step::forward(start, n)`. This version of the trait additionally changes the stepping functions to talk their arguments by value.
As opposed to previous attempts which provided a "step by one" method directly, this version of the trait only exposes "step by n". There are a few reasons for this:
- `Range*`, the primary consumer of `Step`, assumes that the "step by n" operation is cheap. If a single step function is provided, it will be a lot more enticing to implement "step by n" as n repeated calls to "step by one". While this is not strictly incorrect, this behavior would be surprising for anyone used to using `Range<{primitive integer}>`.
- With a trivial default impl, this can be easily added backwards-compatibly later.
- The debug-wrapping "step by n" needs to exist for `RangeFrom` to be consistent between "step by n" and "step by one" operation. (Note: the behavior is not changed by this PR, but making the behavior consistent is made tenable by this PR.)
Three "kinds" of step are provided: `_checked`, which returns an `Option` indicating attempted overflow; (unsuffixed), which provides "safe overflow" behavior (is allowed to panic, wrap, or saturate, depending on what is most convenient for a given type); and `_unchecked`, which is a version which assumes overflow does not happen.
Review is appreciated to check that:
- The invariants as described on the `Step` functions are enough to specify the "common sense" consistency for successor/predecessor.
- Implementation of `Step` functions is correct in the face of overflow and the edges of representable integers.
- Added tests of `Step` functions are asserting the correct behavior (and not just the implemented behavior).
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Add const examples
I only added them to `std::f32` to get feedback on this approach before adding the other constants.
When looking at https://github.com/rust-lang/rust/pull/68952, I found the docs a little confusing. Unless you're intimately aware of what's going on here, I don't think it's super clear what is deprecated and what you're supposed to do instead. I think short examples really clarify what's meant here, so that's what I did.
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Stabilizes the following signed integer functions with saturation
mechanics:
* saturating_abs()
* saturating_neg()
Closes #59983
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I believe that this is a copy/paste error; this example was using f32,
but it's the docs for f64.
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And also point people to use the associated constants of f32 instead.
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Implement BitOr and BitOrAssign for the NonZero integer types
This provides overloaded operators for `NonZero$Int | NonZero$Int`, `NonZero$Int | $Int`, and `$Int | NonZero$Int`. It also provides `BitOrAssign` where `self` is `NonZero$Int`, for symmetry.
It's a pretty small conceptual addition, but is good becasue but avoids a case where the operation is obviously sound, but you'd otherwise need unsafe to do it.
In crates trying to minimize `unsafe` usage, this is unfortunate and makes working with `NonZero` types often not worth it, even if the operations you're doing are clearly sound.
I've marked these as stable as I've been told in the past that trait impls are automatically stable. I'm happy to change it to unstable if this wasn't correct information.
I'm not entirely confident what version I should have put down, so I followed https://www.whatrustisit.com. Hopefully it's correct for this.
Apologies in advance if this has come up before, but I couldn't find it.
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