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# Nursery - A Rust concurrency primitive.

An implementation of Nathaniel J. Smiths Structured Concurrency model:
[Notes on Structured Concurrency](https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/#nurseries-a-structured-replacement-for-go-statements).

# Description

The building block of concurrency is called a `Nursery`. They can adopt or schedule
concurrent operations. Before a `Nursery` is dropped it will block on all of it's
pending concurrent operations. A `Nursery` is itself a concurrent operation so
it can be adopted by another `Nursery` to form a hierarchy.

# Example

```rust
extern crate nursery;
use nursery::thread::{Handle, Pending};
use nursery::{Nursery, Waitable};
use std::sync::Arc;
use std::sync::Mutex;

pub struct Counter {
    count: i32,
}

impl Counter {
    pub fn incr(&mut self) {
        self.count += 1;
    }
}

let counter = Arc::new(Mutex::new(Counter { count: 0 }));
{
    let h_counter = counter.clone();
    let h1 = Pending::new(move || {
        let mut c = h_counter.lock().unwrap();
        c.incr();
    });
    let h_counter = counter.clone();
    let h2 = Pending::new(move || {
        let mut c = h_counter.lock().unwrap();
        c.incr();
    });
    let mut child = Nursery::new();
    child.schedule(Box::new(h1));
    child.schedule(Box::new(h2));
    let mut parent = Nursery::new();
    parent.adopt(child.into());
    // Before parent is dropped all of the above concurrent operations
    // will complete.
}
assert_eq!(counter.lock().unwrap().count, 2);
```