Implement mul for P

1 files changed, 27 insertions, 2 deletions

diff --git a/src/poly.rs b/src/poly.rs
index 34444b3..3f298cb 100644
--- a/src/poly.rs
+++ b/src/poly.rs
@@ -4,8 +4,8 @@ use crate::number::Number;
 use iter::Iter;
 use std::cmp;
 use std::cmp::Ordering;
-use std::ops::{Add, Sub};
-use std::iter::{Zip, Take};
+use std::ops::{Add, Sub, Mul};
+use std::iter::{Sum, Zip, Take};
 
 #[derive(PartialEq, Debug)]
 pub struct P(Vec<Number>);
@@ -47,6 +47,24 @@ impl Sub for &P {
     }
 }
 
+impl Mul for &P {
+    type Output = P;
+
+    fn mul(self, other: Self) -> P {
+        let mut r = Vec::new();
+        for i in 0..other.degree() + 1 {
+            let mut prefix = vec![0.0; i];
+            let mut suffix: Vec<Number> = self.iter()
+                .take(self.degree() + 1)
+                .map(|x| {x * other.0[i]})
+                .collect();
+            prefix.append(&mut suffix);
+            r.push(P(prefix));
+        }
+        r.iter().fold(P(vec![0.0]), |acc, x| &acc + x)
+    }
+}
+
 //****************************REFACTORING************************************
 
 pub type Poly = Vec<Number>;
@@ -135,6 +153,13 @@ mod tests {
     use super::*;
 
     #[test]
+    fn mul_test() {
+        let a = P(vec![1.0, 2.0, 3.0]);
+        let b = P(vec![1.0, 2.0]);
+        assert_eq!(&a * &b, P(vec![1.0, 4.0, 7.0, 6.0]));
+    }
+
+    #[test]
     fn add_test() {
         let a = P(vec![1.0]);
         let b = P(vec![0.0, 0.0, 0.0, 1.0]);