gistfile1.rs

// The number of keys is chosen to vary between d and 2d, where d is the
// minimum number of keys and d+1 is the minimum degree (branching factor) of
// the tree. In this case, d = 2 which results in degree = 5.
static BTreeDegree : uint = 5;

pub struct BTree<K, V> {
    priv pairs: [NodeContent<K, V>, ..BTreeDegree],
}

enum NodeContent<K, V> {
    None,
    BTreeNode { key: K, value: ~BTree<K, V> },
    BTreeValue { key: K, value: V },
}

impl<K: Eq + Ord + TotalOrd, V> BTree<K, V> {
    pub fn new() -> BTree<K, V> {
        BTree { pairs: [None, ..BTreeDegree] }
    }

    pub fn insert(&mut self, key: K, value: V) {
        fail!("fail!");
    }
}


fn main() {
    let mut tree = BTree { pairs: [None, ..BTreeDegree] };
    tree.insert(0, "hi");
    tree.insert(1, "bye");
}

/*
:!rustc test.rs 
test.rs:18:24: 18:28 error: copying a value of non-copyable type `NodeContent<T,U>`
test.rs:18         BTree { pairs: [None, ..BTreeDegree] }
                                   ^~~~
test.rs:18:24: 18:28 note: repeated element will be copied
test.rs:18         BTree { pairs: [None, ..BTreeDegree] }
                                   ^~~~
error: aborting due to previous error
*/

gistfile2.rs

// The number of keys is chosen to vary between d and 2d, where d is the
// minimum number of keys and d+1 is the minimum degree (branching factor) of
// the tree. In this case, d = 2 which results in degree = 5.
static BTreeDegree : uint = 5;

pub struct BTree<K, V> {
    priv pairs: [NodeContent<K, V>, ..BTreeDegree],
}

impl<K: Eq + Ord + TotalOrd, V> Clone for BTree<K, V> {
    #[inline]
    fn clone(&self) -> BTree<K, V> {
        //BTree { pairs: *self.pairs.clone() }
        BTree::new()
    }
}

#[deriving(Clone)]
enum NodeContent<K, V> {
    None,
    BTreeNode { key: K, value: ~BTree<K, V> },
    BTreeValue { key: K, value: V },
}

impl<K: Eq + Ord + TotalOrd, V> BTree<K, V> {
    pub fn new() -> BTree<K, V> {
        BTree { pairs: [None, ..BTreeDegree] }
    }

    pub fn insert(&mut self, key: K, value: V) {
        fail!("fail!");
    }
}


fn main() {
    let mut tree = BTree { pairs: [None, ..BTreeDegree] };
    tree.insert(0, "hi");
    tree.insert(1, "bye");
}

/*

:!rustc test.rs 
test.rs:18:11: 18:16 error: failed to find an implementation of trait std::cmp::Eq for T
test.rs:18 #[deriving(Clone)]
                      ^~~~~
*/