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|
//! Internal utilities.
use std::cmp::Ordering;
/// A wrapper that converts a partial ordering into a total one by panicking.
#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
pub struct Ordered<T>(T);
impl<T> Ordered<T> {
/// Wrap a value.
pub fn new(item: T) -> Self {
Self(item)
}
}
impl<T> From<T> for Ordered<T> {
fn from(item: T) -> Self {
Self::new(item)
}
}
impl<T: PartialOrd> Ord for Ordered<T> {
fn cmp(&self, other: &Self) -> Ordering {
self.partial_cmp(other).expect("Comparison between unordered items")
}
}
impl<T: PartialEq> Eq for Ordered<T> {}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_ordered() {
let one = Ordered::new(1.0);
let two = Ordered::new(2.0);
assert_eq!(one.cmp(&one), Ordering::Equal);
assert_eq!(one.cmp(&two), Ordering::Less);
assert_eq!(two.cmp(&one), Ordering::Greater);
}
#[test]
#[should_panic(expected = "Comparison between unordered items")]
fn test_unordered() {
let one = Ordered::new(1.0);
let nan = Ordered::new(f64::NAN);
assert!(!(one < nan));
assert!(!(nan < one));
let _ = one.cmp(&nan);
}
}
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