diff --git a/Cargo.toml b/Cargo.toml
index 3431415..c740b9c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,6 @@ version = "0.1.0"
 authors = ["Thomas Forgione <thomas@tforgione.fr>"]
 
 [dependencies]
-num = "*"
 
 [[bin]]
 name = "kdtree-example"
diff --git a/src/example.rs b/src/example.rs
index 5f22feb..1c89d1f 100644
--- a/src/example.rs
+++ b/src/example.rs
@@ -1,45 +1,26 @@
-extern crate num;
 extern crate kdtree;
 
 use std::fmt;
-use std::ops::Index;
 
-use kdtree::Zero;
 use kdtree::KdTree;
 
-#[derive(Copy, Clone)]
+#[derive(Clone)]
 struct Vector2 {
     data: [f64; 2],
 }
 
 impl Vector2 {
     pub fn new(x: f64, y: f64) -> Vector2 {
-        Vector2 {
-            data: [x, y],
-        }
-    }
-}
-
-impl Index<usize> for Vector2 {
-    type Output = f64;
-    fn index(&self, index: usize) -> &f64 {
-        &self.data[index]
-    }
-}
-
-impl Zero for Vector2 {
-    fn zero() -> Vector2 {
-        Vector2::new(0.0, 0.0)
+        Vector2 { data: [x, y] }
     }
 }
 
 impl fmt::Display for Vector2 {
     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
-        write!(formatter, "({}, {})", self[0], self[1])
+        write!(formatter, "({}, {})", self.data[0], self.data[1])
     }
 }
 
-
 fn main() {
     let mut points = vec![
         Vector2::new(2.0, 3.0),
@@ -50,8 +31,12 @@ fn main() {
         Vector2::new(7.0, 2.0),
     ];
 
-    let kdtree = KdTree::new(&mut points, 2, 1);
+    let kdtree = KdTree::new(
+        &mut points,
+        2,
+        |coord, ref a, ref b| a.data[coord].partial_cmp(&b.data[coord]).unwrap(),
+        1,
+    );
 
     println!("{}", kdtree);
-
 }
diff --git a/src/lib.rs b/src/lib.rs
index bacd90d..395fdb1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,76 +1,96 @@
-extern crate num;
-
 use std::fmt;
-use std::ops::Index;
-use std::cmp::PartialOrd;
-
-pub trait Zero {
-    fn zero() -> Self;
-}
-
-impl<T: num::Zero> Zero for T {
-    fn zero() -> Self {
-        num::Zero::zero()
-    }
-}
+use std::cmp::Ordering;
 
 /// A k-dimension kd tree
 pub enum KdTree<T> {
-    Node { location: T, left:  Box<KdTree<T>>, right: Box<KdTree<T>> },
+    Node {
+        location: T,
+        left: Box<KdTree<T>>,
+        right: Box<KdTree<T>>,
+    },
     Leaf(Vec<T>),
 }
 
-impl<T, U> KdTree<T> where T: Copy + Clone + Index<usize, Output = U> + Zero, U: PartialOrd {
-    pub fn new(points: &mut [T], dimension: usize, leaf_size: usize) -> KdTree<T> {
-        KdTree::new_with_depth(points, dimension, leaf_size, 0)
+impl<T: Clone> KdTree<T> where {
+    pub fn new<F: Fn(usize, &T, &T) -> Ordering>(
+        points: &mut [T],
+        dimension: usize,
+        comparator: F,
+        leaf_size: usize,
+    ) -> KdTree<T> {
+        KdTree::new_with_depth(points, dimension, &comparator, leaf_size, 0)
     }
 
-    fn new_with_depth(points: &mut [T], dimension: usize, leaf_size: usize, depth: usize) -> KdTree<T> {
-
+    fn new_with_depth<F: Fn(usize, &T, &T) -> Ordering>(
+        points: &mut [T],
+        dimension: usize,
+        comparator: &F,
+        leaf_size: usize,
+        depth: usize,
+    ) -> KdTree<T> {
         // Select axis to work on
         let axis = depth % dimension;
 
         // Sort the points by axis
-        points.sort_by(|p1, p2| p1[axis].partial_cmp(&p2[axis]).unwrap());
+        points.sort_by(|a, b| comparator(axis, a, b));
 
         // Find the median
         let len = points.len();
 
         // If there are not enough elements for a leaf, make a leaf
         if len <= leaf_size {
-            let mut contained = vec![Zero::zero(); len];
-            contained.copy_from_slice(points);
+            let mut contained = vec![];
+            for p in points {
+                contained.push(p.clone());
+            }
             return KdTree::Leaf(contained);
         }
 
         // Else split what's remaining
         let delimiter = points.len() / 2;
-        let median = points[delimiter];
+        let median = points[delimiter].clone();
 
         // Build the left and right branches
-        let zero = Zero::zero();
-        let mut left = vec![zero; delimiter];
-        left.copy_from_slice(&points[0..delimiter]);
+        let mut left = vec![];
+        for i in &points[0..delimiter] {
+            left.push(i.clone());
+        }
 
-        let right = &mut points[delimiter + 1 .. len];
+        let right = &mut points[delimiter + 1..len];
 
         // Recursive call
         KdTree::Node {
             location: median,
-            left:  Box::new(KdTree::new_with_depth(&mut left, dimension, leaf_size, depth + 1)),
-            right: Box::new(KdTree::new_with_depth(right, dimension, leaf_size, depth + 1)),
+            left: Box::new(KdTree::new_with_depth(
+                &mut left,
+                dimension,
+                comparator,
+                leaf_size,
+                depth + 1,
+            )),
+            right: Box::new(KdTree::new_with_depth(
+                right,
+                dimension,
+                comparator,
+                leaf_size,
+                depth + 1,
+            )),
         }
     }
 }
 
-impl<T: Zero + Copy + Clone + fmt::Display + Index<usize>> KdTree<T> {
+impl<T: fmt::Display> KdTree<T> {
     fn print(&self, formatter: &mut fmt::Formatter, indent: &str) -> fmt::Result {
         match self {
-            &KdTree::Node { location, ref left, ref right } => {
+            &KdTree::Node {
+                ref location,
+                ref left,
+                ref right,
+            } => {
                 writeln!(formatter, "{}{}", indent, location)?;
                 left.print(formatter, &format!("{}  ", indent))?;
                 right.print(formatter, &format!("{}  ", indent))?;
-            },
+            }
 
             &KdTree::Leaf(ref elements) => {
                 write!(formatter, "{}[", indent)?;
@@ -78,16 +98,15 @@ impl<T: Zero + Copy + Clone + fmt::Display + Index<usize>> KdTree<T> {
                     write!(formatter, "{}, ", element)?;
                 }
                 writeln!(formatter, "]")?;
-            },
+            }
         }
 
         Ok(())
     }
 }
 
-impl<T: Zero + Copy + Clone + fmt::Display + Index<usize>> fmt::Display for KdTree<T> {
+impl<T: fmt::Display> fmt::Display for KdTree<T> {
     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         self.print(formatter, "")
     }
-
 }