From 6bbd9039ab955017baac7de23d2ae725f8c3c846 Mon Sep 17 00:00:00 2001
From: Daniel Krawisz <danielkrawisz@protonmail.com>
Date: Mon, 31 Oct 2022 20:30:43 -0500
Subject: [PATCH] fix bug in priority_queue==

---
 include/data/tools/priority_queue.hpp |  5 ++++-
 test/CMakeLists.txt                   |  1 +
 test/testPriorityQueue.cpp            | 19 +++++++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 test/testPriorityQueue.cpp

diff --git a/include/data/tools/priority_queue.hpp b/include/data/tools/priority_queue.hpp
index 80ecf8d5..c8697b10 100644
--- a/include/data/tools/priority_queue.hpp
+++ b/include/data/tools/priority_queue.hpp
@@ -66,7 +66,10 @@ namespace data::tool {
     
     template <functional::tree tree, typename element = element_of<tree>> 
     bool inline operator==(const priority_queue<tree, element> a, const priority_queue<tree, element> b) {
-        return a.first() == b.first() && a.rest() == b.rest();
+        if (data::empty(a) && data::empty(b)) return true;
+        if (data::empty(a) || data::empty(b)) return false;
+        if (a.first() != b.first()) return false;
+        return a.rest() == b.rest();
     }
     
     template <functional::tree tree, typename element> 
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 16ecfa87..60e21730 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -37,6 +37,7 @@ package_add_test(testTake testTake.cpp)
 package_add_test(testSort testSort.cpp)
 package_add_test(testLinkedTree testLinkedTree.cpp)
 package_add_test(testMap testMap.cpp)
+package_add_test(testPriorityQueue testPriorityQueue.cpp)
 package_add_test(testForEach testForEach.cpp)
 package_add_test(testPolynomial testPolynomial.cpp)
 package_add_test(testPermutation testPermutation.cpp)
diff --git a/test/testPriorityQueue.cpp b/test/testPriorityQueue.cpp
new file mode 100644
index 00000000..8cd171e8
--- /dev/null
+++ b/test/testPriorityQueue.cpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2019 Daniel Krawisz
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "data/tools.hpp"
+#include "gtest/gtest.h"
+
+TEST(PriorityQueueTest, TestPriorityQueue) {
+    using namespace data;
+    
+    using pq = priority_queue<int>;
+    
+    EXPECT_EQ(pq{}, pq{});
+    EXPECT_EQ(first(pq{} << 1), 1);
+    EXPECT_NE(pq{} << 1, pq{});
+    EXPECT_EQ(pq{} << 1 << 2, pq{} << 2 << 1);
+    EXPECT_EQ(1, first(pq{} << 2 << 1));
+}
+