From adc73d6d5f3354da5b95283279e06e615e848738 Mon Sep 17 00:00:00 2001
From: HenryLee <lee0906@hotmail.com>
Date: Mon, 29 May 2017 18:52:53 +1000
Subject: [PATCH] Fix the arithmetic mistakes in reverse iterator

---
 src/json.hpp                 |  6 +++---
 test/src/unit-iterators2.cpp | 28 ++++++++++++++--------------
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/src/json.hpp b/src/json.hpp
index 902d80f6..fb2740ab 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -8672,7 +8672,7 @@ class basic_json
         json_reverse_iterator operator+(difference_type i) const
         {
             auto result = *this;
-            result += i;
+            result -= i;
             return result;
         }
 
@@ -8680,14 +8680,14 @@ class basic_json
         json_reverse_iterator operator-(difference_type i) const
         {
             auto result = *this;
-            result -= i;
+            result += i;
             return result;
         }
 
         /// return difference
         difference_type operator-(const json_reverse_iterator& other) const
         {
-            return this->base() - other.base();
+            return other.base() - this->base();
         }
 
         /// access to successor
diff --git a/test/src/unit-iterators2.cpp b/test/src/unit-iterators2.cpp
index d9f43e2f..3b767211 100644
--- a/test/src/unit-iterators2.cpp
+++ b/test/src/unit-iterators2.cpp
@@ -747,7 +747,7 @@ TEST_CASE("iterators 2")
                     it += 3;
                     CHECK((j_array.rbegin() + 3) == it);
                     CHECK((it - 3) == j_array.rbegin());
-                    CHECK((j_array.rbegin() - it) == 3);
+                    CHECK((it - j_array.rbegin()) == 3);
                     CHECK(*it == json(3));
                     it -= 2;
                     CHECK(*it == json(5));
@@ -757,7 +757,7 @@ TEST_CASE("iterators 2")
                     it += 3;
                     CHECK((j_array.crbegin() + 3) == it);
                     CHECK((it - 3) == j_array.crbegin());
-                    CHECK((j_array.crbegin() - it) == 3);
+                    CHECK((it - j_array.crbegin()) == 3);
                     CHECK(*it == json(3));
                     it -= 2;
                     CHECK(*it == json(5));
@@ -769,9 +769,9 @@ TEST_CASE("iterators 2")
                 {
                     auto it = j_null.rbegin();
                     it += 3;
-                    CHECK((j_null.rbegin() + 3) == it);
-                    CHECK((it - 3) == j_null.rbegin());
-                    CHECK((j_null.rbegin() - it) == 3);
+                    CHECK((j_null.rbegin() - 3) == it);
+                    CHECK((it + 3) == j_null.rbegin());
+                    CHECK((it - j_null.rbegin()) == 3);
                     CHECK(it != j_null.rend());
                     it -= 3;
                     CHECK(it == j_null.rend());
@@ -779,9 +779,9 @@ TEST_CASE("iterators 2")
                 {
                     auto it = j_null.crbegin();
                     it += 3;
-                    CHECK((j_null.crbegin() + 3) == it);
-                    CHECK((it - 3) == j_null.crbegin());
-                    CHECK((j_null.crbegin() - it) == 3);
+                    CHECK((j_null.crbegin() - 3) == it);
+                    CHECK((it + 3) == j_null.crbegin());
+                    CHECK((it - j_null.crbegin()) == 3);
                     CHECK(it != j_null.crend());
                     it -= 3;
                     CHECK(it == j_null.crend());
@@ -793,9 +793,9 @@ TEST_CASE("iterators 2")
                 {
                     auto it = j_value.rbegin();
                     it += 3;
-                    CHECK((j_value.rbegin() + 3) == it);
-                    CHECK((it - 3) == j_value.rbegin());
-                    CHECK((j_value.rbegin() - it) == 3);
+                    CHECK((j_value.rbegin() - 3) == it);
+                    CHECK((it + 3) == j_value.rbegin());
+                    CHECK((it - j_value.rbegin()) == 3);
                     CHECK(it != j_value.rend());
                     it -= 3;
                     CHECK(*it == json(42));
@@ -803,9 +803,9 @@ TEST_CASE("iterators 2")
                 {
                     auto it = j_value.crbegin();
                     it += 3;
-                    CHECK((j_value.crbegin() + 3) == it);
-                    CHECK((it - 3) == j_value.crbegin());
-                    CHECK((j_value.crbegin() - it) == 3);
+                    CHECK((j_value.crbegin() - 3) == it);
+                    CHECK((it + 3) == j_value.crbegin());
+                    CHECK((it - j_value.crbegin()) == 3);
                     CHECK(it != j_value.crend());
                     it -= 3;
                     CHECK(*it == json(42));