From 98fdddac5d15a25b7ee9a8ca221fe792ac9f2f71 Mon Sep 17 00:00:00 2001
From: Tanner Collin <git@tannercollin.com>
Date: Sat, 14 Mar 2026 17:42:25 -0600
Subject: [PATCH] fix: Correct negative zero logic for +/- and update test

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>
---
 calculator/calculator.app.js | 17 +++++++++++++++--
 calculator/test.js           |  6 +++---
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/calculator/calculator.app.js b/calculator/calculator.app.js
index 4fb4424..2767d01 100644
--- a/calculator/calculator.app.js
+++ b/calculator/calculator.app.js
@@ -532,10 +532,23 @@ function buttonPress(val) {
       break;
     case 'N':
       if (results != null && !hasPressedNumber) {
-        displayOutput(results *= -1);
+        if (results === 0) {
+          results = (1/results === -Infinity || Object.is(results, -0)) ? 0 : -0;
+        } else {
+          results *= -1;
+        }
+        displayOutput(results);
         prevExpression = "-(" + prevExpression + ")";
       } else {
-        displayOutput(currNumber *= -1);
+        if (currNumber === null) currNumber = '0';
+        var num = parseFloat(currNumber);
+        if (num === 0) {
+          // Toggle between 0 and -0
+          currNumber = (1/currNumber === -Infinity || Object.is(currNumber, -0)) ? '0' : -0;
+        } else {
+          currNumber = num * -1;
+        }
+        displayOutput(currNumber);
         currExpression = "-(" + currExpression + ")";
       }
       break;
diff --git a/calculator/test.js b/calculator/test.js
index 12b114a..5c4a89a 100644
--- a/calculator/test.js
+++ b/calculator/test.js
@@ -493,11 +493,11 @@ test('Negative zero handling', () => {
   press('0N'); // get -0
   checkDisplay(-0);
   press('*5');
-  checkDisplay(-0);
+  checkDisplay('5'); // after typing 5, display should be 5
   press('=');
-  checkDisplay(-0);
+  checkDisplay(-0); // -0 * 5 = -0
   buttonPress('R'); buttonPress('R');
-  press('5*-0=');
+  press('5*0N='); // 5 * -0 = -0
   checkDisplay(-0);
 });