Added skeleton implementation of a B-tree with a few bells and

whistles.  No major functionality added yet (such as insertion and
removal).

src/libextra/btree.rs

@@ -0,0 +1,372 @@
+//
+// btree.rs
+// Nif Ward
+// 10/24/13
+//
+// starting implementation of a btree for rust
+// inspired by github user davidhalperin's gist
+
+
+//What's in a BTree?
+pub struct BTree<K, V>{
+    root: Node<K, V>,
+    len: uint,
+    lower_bound: uint,
+    upper_bound: uint
+}
+
+
+impl<K: Clone + TotalOrd, V: Clone> BTree<K, V>{
+    
+    //Returns new BTree with root node (leaf) and user-supplied lower bound
+    fn new(k: K, v: V, lb: uint) -> BTree<K, V>{
+        BTree{
+	    root: Node::new_leaf(~[LeafElt::new(k, v)]),
+	    len: 1,
+	    lower_bound: lb,
+	    upper_bound: 2 * lb
+        }
+    }
+
+    //Helper function for clone
+    fn new_with_node_len(n: Node<K, V>, length: uint, lb: uint) -> BTree<K, V>{
+        BTree{
+	    root: n,
+	    len: length,
+	    lower_bound: lb,
+	    upper_bound: 2 * lb
+	}
+    }
+
+
+    fn clone(&self) -> BTree<K, V>{
+        return BTree::new_with_node_len(self.root.clone(), self.len, self.lower_bound);
+    }
+
+    fn get(self, k: K) -> Option<V>{
+        return self.root.get(k);
+    }
+
+
+    fn add(self, k: K, v: V) -> bool{
+        let is_get = &self.clone().get(k.clone());
+	if is_get.is_some(){ return false; }
+	else{
+	    std::util::replace(&mut self.root.clone(),self.root.add(k.clone(), v));
+	    return true;
+	}
+
+    }
+
+
+
+}
+
+impl<K: ToStr + TotalOrd, V: ToStr> ToStr for BTree<K, V>{
+    //Returns a string representation of the BTree
+    fn to_str(&self) -> ~str{
+        let ret=self.root.to_str();
+	return ret;
+    }
+}
+
+
+//Node types
+enum Node<K, V>{
+    LeafNode(Leaf<K, V>),
+    BranchNode(Branch<K, V>)
+}
+
+
+//Node functions/methods
+impl<K: Clone + TotalOrd, V: Clone> Node<K, V>{
+    //differentiates between leaf and branch nodes
+    fn is_leaf(&self) -> bool{
+        match self{
+	    &LeafNode(*) => true,
+	    &BranchNode(*) => false
+        }
+    }
+    
+    //Creates a new leaf or branch node
+    fn new_leaf(vec: ~[LeafElt<K, V>]) -> Node<K,V>{
+         LeafNode(Leaf::new(vec))
+    }
+    fn new_branch(vec: ~[BranchElt<K, V>], right: ~Node<K, V>) -> Node<K, V>{
+        BranchNode(Branch::new(vec, right))
+    }
+
+    fn get(&self, k: K) -> Option<V>{
+        match *self{
+	    LeafNode(ref leaf) => return leaf.get(k),
+	    BranchNode(ref branch) => return branch.get(k)
+        }
+    }
+
+    //A placeholder for add
+    //Currently returns a leaf node with a single value (the added one)
+    fn add(self, k: K, v: V) -> Node<K, V>{
+        return Node::new_leaf(~[LeafElt::new(k, v)]);
+    }
+}
+
+
+impl<K: Clone + TotalOrd, V: Clone> Clone for Node<K, V>{
+    fn clone(&self) -> Node<K, V>{
+        match *self{
+	    LeafNode(ref leaf) => return Node::new_leaf(leaf.elts.clone()),
+	    BranchNode(ref branch) => return Node::new_branch(branch.elts.clone(), branch.rightmost_child.clone())
+	}
+    }
+}
+
+impl<K: Clone + TotalOrd, V: Clone> TotalOrd for Node<K, V>{
+    #[allow(unused_variable)]
+    fn cmp(&self, other: &Node<K, V>) -> Ordering{
+        //Requires a match statement--defer these procs to branch and leaf.
+        /* if self.elts[0].less_than(other.elts[0]) { return Less}
+	if self.elts[0].greater_than(other.elts[0]) {return Greater}
+	else {return Equal}
+	*/
+	return Equal;
+    }
+}
+
+impl<K: Clone + TotalOrd, V: Clone> TotalEq for Node<K, V>{
+    //Making sure Nodes have TotalEq
+    #[allow(unused_variable)]
+    fn equals(&self, other: &Node<K, V>) -> bool{
+    /* put in a match and defer this stuff to branch and leaf
+
+        let mut shorter = 0;
+        if self.elts.len() <= other.elts.len(){
+	    shorter = self.elts.len();
+	}
+	else{
+	    shorter = other.elts.len();
+	}
+	let mut i = 0;
+	while i < shorter{
+	    if !self.elts[i].has_key(other.elts[i].key){
+	        return false;
+	    }
+	    i +=1;
+        }
+	return true;
+    */
+    return true;
+    }
+}
+
+
+impl<K: ToStr + TotalOrd, V: ToStr> ToStr for Node<K, V>{
+    fn to_str(&self) -> ~str{
+       match *self{
+           LeafNode(ref leaf) => leaf.to_str(),
+	   BranchNode(*) => ~""
+       }
+    }
+}
+
+
+//Array with no children
+struct Leaf<K, V>{
+    elts: ~[LeafElt<K, V>]
+}
+
+//Array of values with children, plus a rightmost child (greater than all)
+struct Branch<K, V>{
+    elts: ~[BranchElt<K,V>],
+    rightmost_child: ~Node<K, V>
+}
+
+
+impl<K: Clone + TotalOrd, V: Clone> Leaf<K, V>{
+    //Constructor takes in a vector of leaves
+    fn new(vec: ~[LeafElt<K, V>]) -> Leaf<K, V>{
+        Leaf{
+            elts: vec
+        }
+    }
+
+
+    fn get(&self, k: K) -> Option<V>{
+        for s in self.elts.iter(){
+	    let order=s.key.cmp(&k);
+	    match order{
+	        Equal => return Some(s.value.clone()),
+		_ => {}
+	    }
+	}
+	return None;
+    }
+
+    //Add method in progress
+    fn add(&self, k: K, v: V) -> Node<K, V>{
+        return Node::new_leaf(~[LeafElt::new(k, v)]);
+    }
+
+}
+
+impl<K: ToStr + TotalOrd, V: ToStr> ToStr for Leaf<K, V>{
+    fn to_str(&self) -> ~str{
+       let mut ret=~"";
+       for s in self.elts.iter(){
+           ret = ret+" // "+ s.to_str();
+       }
+       return ret;
+    }
+
+}
+
+
+impl<K: Clone + TotalOrd, V: Clone> Branch<K, V>{
+    //constructor takes a branch vector and a rightmost child
+    fn new(vec: ~[BranchElt<K, V>], right: ~Node<K, V>) -> Branch<K, V>{
+        Branch{
+	    elts: vec,
+	    rightmost_child: right
+        }
+    }
+
+    fn get(&self, k: K) -> Option<V>{
+        for s in self.elts.iter(){
+	    let order = s.key.cmp(&k);
+	    match order{
+	        Less => return s.left.get(k),
+		Equal => return Some(s.value.clone()),
+		_ => {}
+	    }
+	}
+	return self.rightmost_child.get(k);
+    }
+
+
+    //Add method in progress
+    fn add(&self, k: K, v: V) -> Node<K, V>{
+        return Node::new_leaf(~[LeafElt::new(k, v)]);
+    }
+}
+
+//No left child
+struct LeafElt<K, V>{
+    key: K,
+    value: V
+}
+
+//Has a left child
+struct BranchElt<K, V>{
+    left: Node<K, V>,
+    key: K,
+    value: V
+}
+
+impl<K: Clone + TotalOrd, V> LeafElt<K, V>{
+    fn new(k: K, v: V) -> LeafElt<K, V>{
+        LeafElt{
+            key: k,
+	    value: v
+	}
+    }
+
+    fn less_than(&self, other: LeafElt<K, V>) -> bool{
+        let order = self.key.cmp(&other.key);
+	match order{
+	    Less => true,
+	    _ => false
+	}
+    }
+
+    fn greater_than(&self, other: LeafElt<K, V>) -> bool{
+        let order = self.key.cmp(&other.key);
+	match order{
+	    Greater => true,
+	    _ => false
+	}
+    }
+
+
+    fn has_key(&self, other: K) -> bool{
+        let order = self.key.cmp(&other);
+	match order{
+	    Equal => true,
+	    _ => false
+	}
+    }
+
+}
+
+impl<K: Clone + TotalOrd, V: Clone> Clone for LeafElt<K, V>{
+    fn clone(&self) -> LeafElt<K, V>{
+        return LeafElt::new(self.key.clone(), self.value.clone());
+    }
+}
+
+impl<K: ToStr + TotalOrd, V: ToStr> ToStr for LeafElt<K, V>{
+    fn to_str(&self) -> ~str{
+        return "Key: "+self.key.to_str()+", value: "+self.value.to_str()+"; ";
+    }
+
+}
+
+impl<K: Clone + TotalOrd, V: Clone> BranchElt<K, V>{
+    fn new(k: K, v: V, n: Node<K, V>) -> BranchElt<K, V>{
+        BranchElt{
+            left: n,
+            key: k,
+            value: v
+        }
+    }
+
+    //Add method in progress.  Should it return a branch or a leaf elt?  It will depend on implementation.
+    fn add(&self, k: K, v: V) -> LeafElt<K, V>{
+        return LeafElt::new(k, v);
+    }
+}
+
+impl<K: Clone + TotalOrd, V: Clone> Clone for BranchElt<K, V>{
+    fn clone(&self) -> BranchElt<K, V>{
+        return BranchElt::new(self.key.clone(), self.value.clone(), self.left.clone());
+    }
+}
+
+#[test]
+fn add_test(){
+    let b = BTree::new(1, ~"abc", 2);
+    let is_add = b.add(2, ~"xyz");
+    assert!(is_add);
+
+}
+
+#[test]
+fn get_test(){
+    let b = BTree::new(1, ~"abc", 2);
+    let val = b.get(1);
+    assert_eq!(val, Some(~"abc"));
+}
+
+//Testing LeafElt<K, V> functions (less_than, greater_than, and has_key)
+#[test]
+fn leaf_lt(){
+    let l1 = LeafElt::new(1, ~"abc");
+    let l2 = LeafElt::new(2, ~"xyz");
+    assert!(l1.less_than(l2));
+}
+
+#[test]
+fn leaf_gt(){
+    let l1 = LeafElt::new(1, ~"abc");
+    let l2 = LeafElt::new(2, ~"xyz");
+    assert!(l2.greater_than(l1));
+}
+
+#[test]
+fn leaf_hk(){
+    let l1 = LeafElt::new(1, ~"abc");
+    assert!(l1.has_key(1));
+}
+
+fn main(){
+
+
+}