weak-table-rs: weak hash maps and sets for Rust

This crate defines several kinds of weak hash maps and sets. See the full API documentation.

Usage

```rust use weak_table::WeakHashSet; use std::sync::{Arc, Weak};

type Table = WeakHashSet>;

let mut set = Table::new(); let a = Arc::new("a".tostring()); let b = Arc::new("b".tostring());

set.insert(a.clone());

assert!( set.contains("a") ); assert!( ! set.contains("b") );

set.insert(b.clone());

assert!( set.contains("a") ); assert!( set.contains("b") );

drop(a);

assert!( ! set.contains("a") ); assert!( set.contains("b") ); ```