A library for in-memory collections with flexible and composable indexes.

This crate provides a framework for building collections with multiple indexes that can be combined and composed. Key features include:

• Built-in indexes for common use cases (BTree, HashTable)
• Composable index combinators (grouping, filtering, mapping)
• Aggregation indexes for statistical operations
• Safe and efficient index maintenance as collection changes

Example

use composable_indexes::{Collection, index};

// A struct representing a person
struct Person { name: String, age: u32, occupation: String }

// Create a collection indexed by age using premap
let mut collection = Collection::<Person, _>::new(
  index::zip!(
    index::premap(|p: &Person| p.age, index::btree()),
    index::premap(|p: &Person| p.occupation.clone(), index::hashtable()),
  )
);

// insert & update collection
let alice = collection.insert(Person { name: "Alice".to_string(), age: 30, occupation: "Engineer".to_string() });
collection.insert(Person { name: "Bob".to_string(), age: 25, occupation: "Designer".to_string() });
collection.adjust_mut(alice, |p| { p.age = 31; });
// ...

let q = collection.query();

// Query oldest person
let _youngest = q.0.max_one();

// Query the number of unique occupations
let _occupation_count = q.1.count_distinct();