Scaffold crate to manage data structures

src/backing/keyed/mod.rs

@@ -0,0 +1,39 @@
+/// Data structures for the "keyed" min-queues, supporting priority updates and arbitrary removals, but no duplicates
+use super::pure::PureBacking;
+use std::cmp::Ordering;
+
+/// Helper struct to associate an item with its priority
+#[derive(Debug, Copy, Clone)]
+pub struct Item<D, P: Ord> {
+    data: D,
+    priority: P,
+}
+
+// The relevant Ord implementations are based just on the priority
+impl<D, P: Ord> Ord for Item<D, P> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.priority.cmp(&other.priority)
+    }
+}
+
+impl<D, P: Ord> PartialOrd for Item<D, P> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl<D, P: Ord> PartialEq for Item<D, P> {
+    fn eq(&self, other: &Self) -> bool {
+        self.priority == other.priority
+    }
+}
+
+impl<D, P: Ord> Eq for Item<D, P> {}
+
+/// A data structure usable for backing a "keyed" queue
+pub trait KeyedBacking<D, P: Ord>: PureBacking<Item<D, P>> {
+    /// Update an item's priority
+    fn update(data: D, priority: P) -> Result<(), ()>;
+    /// Remove an item from the queue
+    fn remove(data: D) -> bool;
+}

src/backing/mod.rs

@@ -0,0 +1,2 @@
+pub mod keyed;
+pub mod pure;

src/backing/pure/mod.rs

@@ -0,0 +1,13 @@
+/// Data structures for the "pure" min-queues, supporting duplicates but no arbitrary updates
+
+/// A data structure usable for backing a "pure" queue
+pub trait PureBacking<T: Ord> {
+    /// Instantiates a new data structure
+    fn new() -> Self;
+    /// Places an item into the queue
+    fn add(&mut self, item: T);
+    /// Removes the item with minimum priority, if it exists
+    fn pop(&mut self) -> Option<T>;
+    /// The number of items in the queue
+    fn len(&self) -> usize;
+}

src/lib.rs

@@ -1,3 +1,5 @@
+pub mod backing;
+
 use pyo3::prelude::*;
 
 /// Formats the sum of two numbers as string.