add scale node

src/circuit/dag.rs

@@ -11,6 +11,7 @@ new_key_type! { pub struct NodeId; }
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub enum Node<V: Var> {
     Leaf(V),
+    Scale(NodeId, i32),
     Sum(NodeId, NodeId),
     Prod(NodeId, NodeId),
 }
@@ -19,6 +20,7 @@ impl<V: Var> Node<V> {
     pub fn children(&self) -> impl Iterator<Item = NodeId> {
         match self {
             Node::Leaf(_) => [None, None],
+            Node::Scale(n,_) => [Some(*n), None],
             Node::Sum(l, r) | Node::Prod(l, r) => [Some(*l), Some(*r)],
         }
         .into_iter()