Skip to content

core: make the Rng a by-value parameter of Distribution::sample #160205

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
joboet wants to merge 1 commit into from
Closed

core: make the Rng a by-value parameter of Distribution::sample #160205

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 20 additions & 20 deletions library/core/src/random.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -27,28 +27,28 @@ impl<'a, R: Rng + ?Sized> Rng for &'a mut R {
#[unstable(feature = "random", issue = "130703")]
pub trait Distribution<T> {
/// Samples a random value from the distribution, using the specified random source.
fn sample(&self, source: &mut (impl Rng + ?Sized)) -> T;
fn sample(&self, rng: impl Rng) -> T;
}

impl<T, DT: Distribution<T>> Distribution<T> for &DT {
fn sample(&self, source: &mut (impl Rng + ?Sized)) -> T {
(*self).sample(source)
fn sample(&self, rng: impl Rng) -> T {
(*self).sample(rng)
}
}

impl Distribution<bool> for RangeFull {
fn sample(&self, source: &mut (impl Rng + ?Sized)) -> bool {
let byte: u8 = RangeFull.sample(source);
fn sample(&self, rng: impl Rng) -> bool {
let byte: u8 = RangeFull.sample(rng);
byte & 1 == 1
}
}

macro_rules! impl_full {
($t:ty) => {
impl Distribution<$t> for RangeFull {
fn sample(&self, source: &mut (impl Rng + ?Sized)) -> $t {
fn sample(&self, mut rng: impl Rng) -> $t {
let mut bytes = (0 as $t).to_ne_bytes();
source.fill_bytes(&mut bytes);
rng.fill_bytes(&mut bytes);
<$t>::from_ne_bytes(bytes)
}
}
Expand Down Expand Up @@ -86,16 +86,16 @@ macro_rules! lemire_sample {
// ACM Trans. Model. Comput. Simul. 29, 1, Article 3 (January 2019), 12 pages.
// https://doi.org/10.1145/3230636
// spellchecker:on
fn $name(bound: $ty, source: &mut (impl Rng + ?Sized)) -> $ty {
fn $name(bound: $ty, mut rng: impl Rng) -> $ty {
debug_assert_ne!(bound, 0);

let sample: $ty = (..).sample(source);
let sample: $ty = (..).sample(&mut rng);

let (mut l, mut res) = sample.carrying_mul(bound, 0);
if l < bound {
let t = bound.wrapping_neg() % bound;
while l < t {
let sample: $ty = (..).sample(source);
let sample: $ty = (..).sample(&mut rng);
(l, res) = sample.carrying_mul(bound, 0);
}
}
Expand Down Expand Up @@ -142,7 +142,7 @@ macro_rules! impl_range {
/// use std::random::{Distribution, SystemRng};
/// use std::range::RangeInclusive;
///
/// let roll = RangeInclusive::from(1..=20).sample(&mut SystemRng);
/// let roll = RangeInclusive::from(1..=20).sample(SystemRng);
/// assert!(1 <= roll && roll <= 20);
/// if roll == 20 {
/// println!("Wow! You achieve writing a sound linked list.");
Expand All @@ -151,7 +151,7 @@ macro_rules! impl_range {
/// }
/// ```
#[inline]
fn sample(&self, source: &mut (impl Rng + ?Sized)) -> $unsigned {
fn sample(&self, rng: impl Rng) -> $unsigned {
if self.start > self.last {
empty_range();
}
Expand All @@ -163,14 +163,14 @@ macro_rules! impl_range {
let Some(bound) = (self.last - self.start).checked_add(1) else {
// Overflow can only occur for Self::MIN..=Self::MAX, meaning
// the range is effectively unbounded.
return RangeFull.sample(source);
return RangeFull.sample(rng);
};

let offset = if bound.is_power_of_two() {
let sample: $unsigned = RangeFull.sample(source);
let sample: $unsigned = RangeFull.sample(rng);
sample & (bound - 1)
} else {
$bounded(bound as $base, source) as $unsigned
$bounded(bound as $base, rng) as $unsigned
};

self.start + offset
Expand Down Expand Up @@ -207,7 +207,7 @@ macro_rules! impl_range {
/// use std::random::{Distribution, SystemRng};
/// use std::range::RangeInclusive;
///
/// let roll = RangeInclusive::from(1..=20).sample(&mut SystemRng);
/// let roll = RangeInclusive::from(1..=20).sample(SystemRng);
/// assert!(1 <= roll && roll <= 20);
/// if roll == 20 {
/// println!("Wow! You achieve writing a sound linked list.");
Expand All @@ -216,7 +216,7 @@ macro_rules! impl_range {
/// }
/// ```
#[inline]
fn sample(&self, source: &mut (impl Rng + ?Sized)) -> $signed {
fn sample(&self, rng: impl Rng) -> $signed {
if self.start > self.last {
empty_range();
}
Expand All @@ -229,14 +229,14 @@ macro_rules! impl_range {
else {
// Overflow can only occur for Self::MIN..=Self::MAX, meaning
// the range is effectively unbounded.
return RangeFull.sample(source);
return RangeFull.sample(rng);
};

let offset = if bound.is_power_of_two() {
let sample: $unsigned = RangeFull.sample(source);
let sample: $unsigned = RangeFull.sample(rng);
sample & (bound - 1)
} else {
$bounded(bound as $base, source) as $unsigned
$bounded(bound as $base, rng) as $unsigned
};

self.start.wrapping_add_unsigned(offset)
Expand Down
4 changes: 2 additions & 2 deletions library/std/src/random.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,7 @@ impl Rng for SystemRng {

/// Generates a random value from a distribution, using the default random source.
///
/// This is a convenience function for `dist.sample(&mut SystemRng)` and will sample according to
/// This is a convenience function for `dist.sample(SystemRng)` and will sample according to
/// the same distribution as the underlying [`Distribution`] trait implementation. See [`SystemRng`]
/// for more information about how randomness is sourced.
///
Expand All @@ -98,5 +98,5 @@ impl Rng for SystemRng {
/// [version 4/variant 1 UUID]: https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_(random)
#[unstable(feature = "random", issue = "130703")]
pub fn random<T>(dist: impl Distribution<T>) -> T {
dist.sample(&mut SystemRng)
dist.sample(SystemRng)
}
Loading