From 9ebfeb708718c45d234724acab94fdfb5327bca5 Mon Sep 17 00:00:00 2001
From: Karl Hiner <karl.hiner@gmail.com>
Date: Fri, 5 Aug 2022 14:35:38 -0400
Subject: [PATCH] Add `operator<` to , to allow use as a map key

---
 include/nlohmann/detail/json_pointer.hpp | 22 ++++++++++++++++++++++
 single_include/nlohmann/json.hpp         | 22 ++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/include/nlohmann/detail/json_pointer.hpp b/include/nlohmann/detail/json_pointer.hpp
index 28de45028..bdeae78f0 100644
--- a/include/nlohmann/detail/json_pointer.hpp
+++ b/include/nlohmann/detail/json_pointer.hpp
@@ -862,6 +862,15 @@ class json_pointer
     {
         return *this == json_pointer(rhs);
     }
+
+    /// @brief compares JSON pointer and string for less-than
+    template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+    friend bool operator<(json_pointer<RefStringTypeLhs> const& lhs,
+                          json_pointer<RefStringTypeRhs> const& rhs) noexcept
+    {
+        return lhs.reference_tokens < rhs.reference_tokens;
+    }
+
 #else
     /// @brief compares two JSON pointers for equality
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_eq/
@@ -904,6 +913,12 @@ class json_pointer
     // NOLINTNEXTLINE(readability-redundant-declaration)
     friend bool operator!=(const StringType& lhs,
                            const json_pointer<RefStringTypeRhs>& rhs);
+
+    /// @brief compares string and JSON pointer for less-than
+    template<typename RefStringTypeRhs, typename StringType>
+    // NOLINTNEXTLINE(readability-redundant-declaration)
+    friend bool operator<(const StringType& lhs,
+                          const json_pointer<RefStringTypeRhs>& rhs);
 #endif
 
   private:
@@ -958,6 +973,13 @@ inline bool operator!=(const StringType& lhs,
 {
     return !(lhs == rhs);
 }
+
+template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+inline bool operator<(const json_pointer<RefStringTypeLhs>& lhs,
+                      const json_pointer<RefStringTypeRhs>& rhs) noexcept
+{
+    return lhs.reference_tokens < rhs.reference_tokens;
+}
 #endif
 
 NLOHMANN_JSON_NAMESPACE_END
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index beee0136c..3bf1b92fb 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -14464,6 +14464,15 @@ class json_pointer
     {
         return *this == json_pointer(rhs);
     }
+
+    /// @brief compares JSON pointer and string for less-than
+    template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+    friend bool operator<(json_pointer<RefStringTypeLhs> const& lhs,
+                          json_pointer<RefStringTypeRhs> const& rhs) noexcept
+    {
+        return lhs.reference_tokens < rhs.reference_tokens;
+    }
+
 #else
     /// @brief compares two JSON pointers for equality
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_eq/
@@ -14506,6 +14515,12 @@ class json_pointer
     // NOLINTNEXTLINE(readability-redundant-declaration)
     friend bool operator!=(const StringType& lhs,
                            const json_pointer<RefStringTypeRhs>& rhs);
+
+    /// @brief compares string and JSON pointer for less-than
+    template<typename RefStringTypeRhs, typename StringType>
+    // NOLINTNEXTLINE(readability-redundant-declaration)
+    friend bool operator<(const StringType& lhs,
+                          const json_pointer<RefStringTypeRhs>& rhs);
 #endif
 
   private:
@@ -14560,6 +14575,13 @@ inline bool operator!=(const StringType& lhs,
 {
     return !(lhs == rhs);
 }
+
+template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+inline bool operator<(const json_pointer<RefStringTypeLhs>& lhs,
+                      const json_pointer<RefStringTypeRhs>& rhs) noexcept
+{
+    return lhs.reference_tokens < rhs.reference_tokens;
+}
 #endif
 
 NLOHMANN_JSON_NAMESPACE_END