81bb4ef300
# Objective - Slight documentation tweak to make it more clear that `FloatOrd` also implements `Hash` and `Eq`, not just `Ord`. - I know that it does show that Hash is implemented in the docs, but I had missed it after reading the description and assuming it didn't do it, so hopefully this helps other people who might miss it like I did. :) ## Solution - Just mention in the Hash and Eq implementation in the docstring.
67 lines
1.8 KiB
Rust
67 lines
1.8 KiB
Rust
use std::{
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cmp::Ordering,
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hash::{Hash, Hasher},
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ops::Neg,
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};
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/// A wrapper for floats that implements [`Ord`], [`Eq`], and [`Hash`] traits.
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///
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/// This is a work around for the fact that the IEEE 754-2008 standard,
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/// implemented by Rust's [`f32`] type,
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/// doesn't define an ordering for [`NaN`](f32::NAN),
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/// and `NaN` is not considered equal to any other `NaN`.
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///
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/// Wrapping a float with `FloatOrd` breaks conformance with the standard
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/// by sorting `NaN` as less than all other numbers and equal to any other `NaN`.
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#[derive(Debug, Copy, Clone, PartialOrd)]
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pub struct FloatOrd(pub f32);
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#[allow(clippy::derive_ord_xor_partial_ord)]
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impl Ord for FloatOrd {
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fn cmp(&self, other: &Self) -> Ordering {
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self.0.partial_cmp(&other.0).unwrap_or_else(|| {
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if self.0.is_nan() && !other.0.is_nan() {
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Ordering::Less
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} else if !self.0.is_nan() && other.0.is_nan() {
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Ordering::Greater
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} else {
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Ordering::Equal
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}
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})
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}
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}
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impl PartialEq for FloatOrd {
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fn eq(&self, other: &Self) -> bool {
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if self.0.is_nan() && other.0.is_nan() {
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true
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} else {
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self.0 == other.0
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}
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}
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}
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impl Eq for FloatOrd {}
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impl Hash for FloatOrd {
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fn hash<H: Hasher>(&self, state: &mut H) {
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if self.0.is_nan() {
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// Ensure all NaN representations hash to the same value
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state.write(&f32::to_ne_bytes(f32::NAN));
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} else if self.0 == 0.0 {
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// Ensure both zeroes hash to the same value
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state.write(&f32::to_ne_bytes(0.0f32));
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} else {
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state.write(&f32::to_ne_bytes(self.0));
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}
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}
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}
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impl Neg for FloatOrd {
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type Output = FloatOrd;
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fn neg(self) -> Self::Output {
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FloatOrd(-self.0)
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}
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}
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