Initial commit

Starting off with a function able to turn recursive linear
interpolations into their corresponding polynomial.

1 files changed, 53 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..31f230e
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,53 @@
+pub type Number = f32;
+
+pub type Poly = Vec<Number>;
+
+#[derive(Debug)]
+pub enum Lerp {
+    Node(Box<Lerp>, Box<Lerp>),
+    Leaf(Number, Number)
+}
+
+impl Lerp {
+    pub fn new(v: Vec<Number>) -> Box<Lerp> {
+        Lerp::new_s(&v[..])
+    }
+
+    fn new_s(v: &[Number]) -> Box<Lerp> {
+        match v.len() {
+            0 => Box::new(Lerp::Leaf(0.0, 0.0)),
+            1 => Box::new(Lerp::Leaf(v[0], v[0])),
+            2 => Box::new(Lerp::Leaf(v[0], v[1])),
+            _ => Box::new(Lerp::Node(Lerp::new_s(&v[0..v.len() - 1]), Lerp::new_s(&v[1..v.len()])))
+        }
+    }
+}
+
+pub fn lp(l: Box<Lerp>) -> Poly {
+    match *l {
+        Lerp::Leaf(a, b) => vec![a, b - a],
+        Lerp::Node(a, b) => {
+            let a = lp(a);
+            let b = lp(b);
+            let c = poly_sub(&b, &a);
+            skewed_sum(a, c)
+        }
+    }
+}
+
+fn poly_sub(a: &Poly, b: &Poly) -> Poly {
+    let mut r = a.clone();
+    for i in 0..r.len() {
+        r[i] -= b[i];
+    }
+    r
+}
+
+fn skewed_sum(a: Poly, b: Poly) -> Poly {
+    let mut r = a.clone();
+    for i in 0..r.len() - 1 {
+        r[i + 1] += b[i];
+    }
+    r.push(b[b.len() - 1]);
+    r
+}