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Added a Distribution<usize> for Poisson #958

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CGMossa wants to merge 2 commits into from
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Added a Distribution<usize> for Poisson #958

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385a2d5
Added a Distribution<usize> for Poisson
CGMossa Apr 2, 2020
fca9cda
Added to_usize
CGMossa Apr 2, 2020
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6 changes: 3 additions & 3 deletions rand_distr/src/poisson.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -138,7 +138,7 @@ where Standard: Distribution<N>
}

impl<N: Float> Distribution<u64> for Poisson<N>
where Standard: Distribution<N>
where Standard: Distribution<N>
{
#[inline]
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u64 {
Expand All @@ -152,8 +152,8 @@ impl<N: Float> Distribution<usize> for Poisson<N>
{
#[inline]
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize {
let result: u64 = self.sample(rng);
result as usize
let result: N = self.sample(rng);
result.to_usize().unwrap()
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@vks vks May 1, 2020 •
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This may panic on 32-bit platforms. Maybe we should document that somewhere?

}
}

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20 changes: 20 additions & 0 deletions rand_distr/src/utils.rs
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Expand Up @@ -42,6 +42,9 @@ pub trait Float:
/// Support converting to an unsigned integer.
fn to_u64(self) -> Option<u64>;

/// Support converting to an unsigned integer.
fn to_usize(self) -> Option<usize>;

/// Take the absolute value of self
fn abs(self) -> Self;
/// Take the largest integer less than or equal to self
Expand Down Expand Up @@ -82,6 +85,15 @@ impl Float for f32 {
}
}

#[inline]
fn to_usize(self) -> Option<usize> {
if self >= 0. && self <= ::core::usize::MAX as f32 {
Comment on lines +89 to +90
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@dhardy dhardy Apr 5, 2020

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This is incorrect for 32-bit platforms. Check this out.

This isn't your fault; to_u64 for f64 makes the same mistake. Hmm, even the TryFrom in Rust 1.34 doesn't handle this conversion. I'm starting to hate this topic; seems simple but isn't.

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@CGMossa CGMossa May 1, 2020

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Ohh this issue. I don't know how to solve this aswell. The link didn't suggest a solution. I think this belongs in another PR, or something?

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@dhardy dhardy May 1, 2020

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Yes: #973

Some(self as usize)
} else {
None
}
}

#[inline]
fn abs(self) -> Self {
self.abs()
Expand Down Expand Up @@ -145,6 +157,14 @@ impl Float for f64 {
None
}
}
#[inline]
fn to_usize(self) -> Option<usize> {
if self >= 0. && self <= ::core::usize::MAX as f64 {
Some(self as usize)
} else {
None
}
}

#[inline]
fn abs(self) -> Self {
Expand Down