add sub ops for flat polynomial

src/bin/flat.rs

@@ -1,34 +1,17 @@
 use circuit_polynomial::poly::flat;
-use circuit_polynomial::poly::flat::Mono;
+use circuit_polynomial::var;
-use circuit_polynomial::{var,poly::var::StaticVar};
 
 fn main() {
-    let poly: flat::Poly<StaticVar> = [
+    let poly = (2
-        (
+        * ((var!("x", 1, 5) ^ 5) * (var!("x", 1, 2) ^ 5) * (var!("x", 2, 5) ^ 1)))
-            2,
+        + (3 * ((var!("x", 1, 9) ^ 5) * (var!("x", 1, 2) ^ 5) * (var!("x", 2, 5) ^ 1)));
-            [
-                (var!("x", 1, 5), 5),
-                (var!("x", 1, 2), 5),
-                (var!("x", 2, 5), 1),
-            ],
-        ),
-        (
-            3,
-            [
-                (var!("x", 1, 9), 5),
-                (var!("x", 1, 2), 5),
-                (var!("x", 2, 5), 1),
-            ],
-        ),
-    ]
-    .into();
 
     let x = var!("x");
     let y = var!("y");
-    let mono = 3*((&x^2)*(&y^4));
+    let other = -3 * ((&x ^ 2) * (&y ^ 4));
 
     println!("{poly}");
 
-    let z=poly+mono;
+    let z = poly - other;
     println!("{z}");
 }

src/poly/flat.rs

@@ -1,7 +1,7 @@
 use itertools::Itertools;
 use std::fmt::{self, Display};
 
-use std::ops::{Add, BitXor, Mul};
+use std::ops::{Add, Sub, BitXor, Mul};
 
 use super::var::{StaticVar, Var};
 use std::collections::HashMap;
@@ -75,9 +75,11 @@ impl<V: Var, U: Into<V>> FromIterator<(U, u32)> for Mono<V> {
         term.sort();
 
         // Check duplicate variables
-        assert!((term[..])
+        assert!(
+            (term[..])
                 .windows(2)
-            .all(|window| window[0].0 != window[1].0));
+                .all(|window| window[0].0 != window[1].0)
+        );
 
         Mono { term }
     }
@@ -179,3 +181,16 @@ impl<V: Var> Add for Poly<V> {
         self
     }
 }
+
+impl<V: Var> Sub for Poly<V> {
+    type Output = Poly<V>;
+
+    fn sub(mut self, other: Poly<V>) -> Self::Output {
+        for (mono, coeff) in other.mono {
+            let entry = self.mono.entry(mono).or_insert(0);
+            *entry -= coeff;
+        }
+        self.mono.retain(|_, &mut coeff| coeff != 0);
+        self
+    }
+}