Impl ArbitraryOrd for std smart pointers and various generic types #37

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1. tcharding commented on Jan 30, 2025

   

   tcharding

   on Jan 30, 2025

   Last edited by tcharding

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   What is the use case? I tried to think it through for Vec but I got to this code that builds already.

   /// A point in 2D space.
   ///
   /// We do not want users to be able to write `a < b` because it is not well defined.
   #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
   struct Point {
       x: u32,
       y: u32,
   }
   
   impl ArbitraryOrd for Point {
       fn arbitrary_cmp(&self, other: &Self) -> Ordering { (self.x, self.y).cmp(&(other.x, other.y)) }
   }
   
   impl fmt::Display for Point {
       fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "({}, {})", self.x, self.y) }
   }
   
   /// A type that derives `Ord` and friends.
   #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
   struct Adt {
       // point: Point,  // Doesn't build, this is the reason we provide `Ordered`.
       point: Ordered<Point>,
       // v: Vec<Point>, // Also doesn't build but we can wrap in `Ordered` again.
       v: Vec<Ordered<Point>>,
   }
2. Kixunil commented on Jan 31, 2025

   

   Kixunil

   on Jan 31, 2025

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   The use case is being able to write things like BTreeMap<Ordered<Box<HugeStructWithArbitrarryOrd>>> etc. Generally, crates implement their traits for all sensible std types. For Vec, dealing with Ordered<Vec<Point>> is very likely less annoying than Vec<Ordered<Point>.
3. tcharding commented on Feb 3, 2025

   

   tcharding

   on Feb 3, 2025

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   I'm cutting the 1.0-alpha release but flagging that I intend on doing this before 1.0

   👍React with 👍1Reacted by Martin Habovštiak