1 files changed, 123 insertions, 0 deletions
diff --git a/src/poly.rs b/src/poly.rs
new file mode 100644
index 0000000..35e85d8
--- /dev/null
+++ b/src/poly.rs
@@ -0,0 +1,123 @@
+mod iter;
+
+use iter::Iter;
+use std::fmt;
+use std::ops::{Add, Sub};
+
+#[derive(PartialEq, Debug, Clone)]
+pub struct Poly {
+    data: Vec<f32>,
+    degree: usize,
+}
+
+impl Poly {
+    pub fn new(data: Vec<f32>) -> Poly {
+        if data.len() > 1 {
+            let mut i = data.len() - 1;
+            while data[i] == 0.0 && i > 0 {
+                i -= 1;
+            }
+            Poly { data, degree: i }
+        } else {
+            Poly { data, degree: 0 }
+        }
+    }
+
+    pub fn degree(&self) -> usize {
+        self.degree
+    }
+
+    fn iter(&self) -> Iter {
+        Iter::new(self.data.clone(), self.degree())
+    }
+
+    pub fn shift(self) -> Poly {
+        let mut r = vec![0.0];
+        r.append(&mut self.data.clone());
+        Poly::new(r)
+    }
+
+    pub fn deriv(&self) -> Poly {
+        let mut data = vec![0.0; self.degree()];
+        if self.degree() > 0 {
+            for i in 0..self.degree() {
+                data[i] = self.data[i + 1] * (i + 1) as f32;
+            }
+            Poly::new(data)
+        } else {
+            Poly::new(vec![0.0])
+        }
+    }
+}
+
+impl Add for &Poly {
+    type Output = Poly;
+
+    fn add(self, other: Self) -> Poly {
+        Poly::new(self.iter().zip(other.iter()).map(|(x, y)| x + y).collect())
+    }
+}
+
+impl Sub for &Poly {
+    type Output = Poly;
+
+    fn sub(self, other: Self) -> Poly {
+        Poly::new(self.iter().zip(other.iter()).map(|(x, y)| x - y).collect())
+    }
+}
+
+impl fmt::Display for &Poly {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut s = String::new();
+        for i in 0..self.data.len() {
+            s.push_str(&self.data[i].clone().to_string());
+            if i < self.data.len() - 1 {
+                s.push_str(", ");
+            }
+        }
+        write!(f, "{}", s)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn shift_test() {
+        let a = Poly::new(vec![1.0, 2.0, 3.0]);
+        assert_eq!(a.shift(), Poly::new(vec![0.0, 1.0, 2.0, 3.0]));
+    }
+
+    #[test]
+    fn add_test() {
+        let a = Poly::new(vec![1.0]);
+        let b = Poly::new(vec![0.0, 0.0, 0.0, 1.0]);
+        assert_eq!(&a + &b, Poly::new(vec![1.0, 0.0, 0.0, 1.0]));
+    }
+
+    #[test]
+    fn sub_test() {
+        let a = Poly::new(vec![1.0, 2.0, 3.0]);
+        let b = Poly::new(vec![1.0, 1.0, 1.0]);
+        assert_eq!(&a - &b, Poly::new(vec![0.0, 1.0, 2.0]));
+    }
+
+    #[test]
+    fn deriv_test() {
+        let p = Poly::new(vec![1.0, 2.0, 3.0, 4.0]);
+        assert_eq!(p.deriv(), Poly::new(vec![2.0, 6.0, 12.0]));
+    }
+
+    #[test]
+    fn degree_is_five() {
+        let p = Poly::new(vec![0.0, 0.0, 0.0, 0.0, 0.0, 2.0]);
+        assert_eq!(p.degree(), 5);
+    }
+
+    #[test]
+    fn degree_is_zero() {
+        let p = Poly::new(vec![0.0; 6]);
+        assert_eq!(p.degree(), 0);
+    }
+}