fix: recognize unary operators at ParenthesisStart

src/nodes/parse.rs

@@ -151,7 +151,11 @@ impl FromStr for Nodes {
                 } else if c == ')' {
                     nodes.push(Node::ParenthesisEnd);
                 } else {
-                    if matches!(nodes.last(), Some(Node::Operator(_)) | None) {
+                    if matches!(
+                        nodes.last(),
+                        Some(Node::Operator(_) | Node::ParenthesisStart) | None
+                    ) {
+                        // it must be a unary operator
                         state = ParsingState::ReadingNumber(i);
                     } else {
                         nodes.push(Node::Operator(
@@ -218,3 +222,16 @@ fn test_e() {
         ],
     )
 }
+#[test]
+fn test_unary_op() {
+    assert_eq!(
+        Nodes::from_str("5(-5)").unwrap().as_ref(),
+        &[
+            Node::from(5),
+            Node::Operator(Operator::Mult),
+            Node::ParenthesisStart,
+            Node::from(-5),
+            Node::ParenthesisEnd,
+        ],
+    )
+}