Add json_pointer/string_t equality comparison operators (#3664)

docs/examples/json_pointer__operator__equal.cpp

@@ -0,0 +1,19 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // different JSON pointers
+    json::json_pointer ptr0;
+    json::json_pointer ptr1("");
+    json::json_pointer ptr2("/foo");
+
+    // compare JSON pointers
+    std::cout << std::boolalpha
+              << "\"" << ptr0 << "\" == \"" << ptr0 << "\": " << (ptr0 == ptr0) << '\n'
+              << "\"" << ptr0 << "\" == \"" << ptr1 << "\": " << (ptr0 == ptr1) << '\n'
+              << "\"" << ptr1 << "\" == \"" << ptr2 << "\": " << (ptr1 == ptr2) << '\n'
+              << "\"" << ptr2 << "\" == \"" << ptr2 << "\": " << (ptr2 == ptr2) << std::endl;
+}

docs/examples/json_pointer__operator__equal.output

@@ -0,0 +1,4 @@
+"" == "": true
+"" == "": true
+"" == "/foo": false
+"/foo" == "/foo": true

docs/examples/json_pointer__operator__equal_stringtype.cpp

@@ -0,0 +1,33 @@
+#include <exception>
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // different JSON pointers
+    json::json_pointer ptr0;
+    json::json_pointer ptr1("");
+    json::json_pointer ptr2("/foo");
+
+    // different strings
+    std::string str0("");
+    std::string str1("/foo");
+    std::string str2("bar");
+
+    // compare JSON pointers and strings
+    std::cout << std::boolalpha
+              << "\"" << ptr0 << "\" == \"" << str0 << "\": " << (ptr0 == str0) << '\n'
+              << "\"" << str0 << "\" == \"" << ptr1 << "\": " << (str0 == ptr1) << '\n'
+              << "\"" << ptr2 << "\" == \"" << str1 << "\": " << (ptr2 == str1) << std::endl;
+
+    try
+    {
+        std::cout << "\"" << str2 << "\" == \"" << ptr2 << "\": " << (str2 == ptr2) << std::endl;
+    }
+    catch (const json::parse_error& ex)
+    {
+        std::cout << ex.what() << std::endl;
+    }
+}

docs/examples/json_pointer__operator__equal_stringtype.output

@@ -0,0 +1,4 @@
+"" == "": true
+"" == "": true
+"/foo" == "/foo": true
+"bar" == "/foo": [json.exception.parse_error.107] parse error at byte 1: JSON pointer must be empty or begin with '/' - was: 'bar'

docs/examples/json_pointer__operator__notequal.cpp

@@ -0,0 +1,19 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // different JSON pointers
+    json::json_pointer ptr0;
+    json::json_pointer ptr1("");
+    json::json_pointer ptr2("/foo");
+
+    // compare JSON pointers
+    std::cout << std::boolalpha
+              << "\"" << ptr0 << "\" != \"" << ptr0 << "\": " << (ptr0 != ptr0) << '\n'
+              << "\"" << ptr0 << "\" != \"" << ptr1 << "\": " << (ptr0 != ptr1) << '\n'
+              << "\"" << ptr1 << "\" != \"" << ptr2 << "\": " << (ptr1 != ptr2) << '\n'
+              << "\"" << ptr2 << "\" != \"" << ptr2 << "\": " << (ptr2 != ptr2) << std::endl;
+}

docs/examples/json_pointer__operator__notequal.output

@@ -0,0 +1,4 @@
+"" != "": false
+"" != "": false
+"" != "/foo": true
+"/foo" != "/foo": false

docs/examples/json_pointer__operator__notequal_stringtype.cpp

@@ -0,0 +1,32 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // different JSON pointers
+    json::json_pointer ptr0;
+    json::json_pointer ptr1("");
+    json::json_pointer ptr2("/foo");
+
+    // different strings
+    std::string str0("");
+    std::string str1("/foo");
+    std::string str2("bar");
+
+    // compare JSON pointers and strings
+    std::cout << std::boolalpha
+              << "\"" << ptr0 << "\" != \"" << str0 << "\": " << (ptr0 != str0) << '\n'
+              << "\"" << str0 << "\" != \"" << ptr1 << "\": " << (str0 != ptr1) << '\n'
+              << "\"" << ptr2 << "\" != \"" << str1 << "\": " << (ptr2 != str1) << std::endl;
+
+    try
+    {
+        std::cout << "\"" << str2 << "\" != \"" << ptr2 << "\": " << (str2 != ptr2) << std::endl;
+    }
+    catch (const json::parse_error& ex)
+    {
+        std::cout << ex.what() << std::endl;
+    }
+}

docs/examples/json_pointer__operator__notequal_stringtype.output

@@ -0,0 +1,4 @@
+"" != "": false
+"" != "": false
+"/foo" != "/foo": false
+"bar" != "/foo": [json.exception.parse_error.107] parse error at byte 1: JSON pointer must be empty or begin with '/' - was: 'bar'

docs/mkdocs/docs/api/json_pointer/index.md

@@ -29,6 +29,8 @@ are the base for JSON patches.
 - [(constructor)](json_pointer.md)
 - [**to_string**](to_string.md) - return a string representation of the JSON pointer
 - [**operator string_t**](operator_string_t.md) - return a string representation of the JSON pointer
+- [**operator==**](operator_eq.md) - compare: equal
+- [**operator!=**](operator_ne.md) - compare: not equal
 - [**operator/=**](operator_slasheq.md) - append to the end of the JSON pointer
 - [**operator/**](operator_slash.md) - create JSON Pointer by appending
 - [**parent_pointer**](parent_pointer.md) - returns the parent of this JSON pointer

docs/mkdocs/docs/api/json_pointer/operator_eq.md

@@ -0,0 +1,107 @@
+# <small>nlohmann::json_pointer::</small>operator==
+
+```cpp
+// until C++20
+template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+bool operator==(
+    const json_pointer<RefStringTypeLhs>& lhs,
+    const json_pointer<RefStringTypeRhs>& rhs) noexcept;            // (1)
+
+template<typename RefStringTypeLhs, typename StringType>
+bool operator==(
+    const json_pointer<RefStringTypeLhs>& lhs,
+    const StringType& rhs);                                         // (2)
+
+template<typename RefStringTypeRhs, typename StringType>
+bool operator==(
+    const StringType& lhs,
+    const json_pointer<RefStringTypeRhs>& rhs);                     // (2)
+
+// since C++20
+class json_pointer {
+    template<typename RefStringTypeRhs>
+    bool operator==(
+        const json_pointer<RefStringTypeRhs>& rhs) const noexcept;  // (1)
+
+    bool operator==(const string_t& rhs) const;                     // (2)
+};
+```
+
+1. Compares two JSON pointers for equality by comparing their reference tokens.
+
+2. Compares a JSON pointer and a string or a string and a JSON pointer for equality by converting the string to a JSON
+   pointer and comparing the JSON pointers according to 1.
+
+## Template parameters
+
+`RefStringTypeLhs`, `RefStringTypeRhs`
+:   the string type of the left-hand side or right-hand side JSON pointer, respectively
+
+`StringType`
+:   the string type derived from the `json_pointer` operand ([`json_pointer::string_t`](string_t.md))
+
+## Parameters
+
+`lhs` (in)
+:   first value to consider
+
+`rhs` (in)
+:   second value to consider
+
+## Return value
+
+whether the values `lhs`/`*this` and `rhs` are equal
+
+## Exception safety
+
+1. No-throw guarantee: this function never throws exceptions.
+2. Strong exception safety: if an exception occurs, the original value stays intact.
+
+## Exceptions
+
+1. (none)
+2. The function can throw the following exceptions:
+   - Throws [parse_error.107](../../home/exceptions.md#jsonexceptionparse_error107) if the given JSON pointer `s` is
+     nonempty and does not begin with a slash (`/`); see example below.
+   - Throws [parse_error.108](../../home/exceptions.md#jsonexceptionparse_error108) if a tilde (`~`) in the given JSON
+     pointer `s` is not followed by `0` (representing `~`) or `1` (representing `/`); see example below.
+
+## Complexity
+
+Constant if `lhs` and `rhs` differ in the number of reference tokens, otherwise linear in the number of reference
+tokens.
+
+## Examples
+
+??? example "Example: (1) Comparing JSON pointers"
+
+    The example demonstrates comparing JSON pointers.
+        
+    ```cpp
+    --8<-- "examples/json_pointer__operator__equal.cpp"
+    ```
+    
+    Output:
+    
+    ```
+    --8<-- "examples/json_pointer__operator__equal.output"
+    ```
+
+??? example "Example: (2) Comparing JSON pointers and strings"
+
+    The example demonstrates comparing JSON pointers and strings, and when doing so may raise an exception.
+        
+    ```cpp
+    --8<-- "examples/json_pointer__operator__equal_stringtype.cpp"
+    ```
+    
+    Output:
+    
+    ```
+    --8<-- "examples/json_pointer__operator__equal_stringtype.output"
+    ```
+
+## Version history
+
+1. Added in version 2.1.0. Added C++20 member functions in version 3.11.2.
+2. Added in version 3.11.2.

docs/mkdocs/docs/api/json_pointer/operator_ne.md

@@ -0,0 +1,105 @@
+# <small>nlohmann::json_pointer::</small>operator!=
+
+```cpp
+// until C++20
+template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+bool operator!=(
+    const json_pointer<RefStringTypeLhs>& lhs,
+    const json_pointer<RefStringTypeRhs>& rhs) noexcept;  // (1)
+
+template<typename RefStringTypeLhs, typename StringType>
+bool operator!=(
+    const json_pointer<RefStringTypeLhs>& lhs,
+    const StringType& rhs);                               // (2)
+
+template<typename RefStringTypeRhs, typename StringType>
+bool operator!=(
+    const StringType& lhs,
+    const json_pointer<RefStringTypeRhs>& rhs);           // (2)
+```
+
+1. Compares two JSON pointers for inequality by comparing their reference tokens.
+
+2. Compares a JSON pointer and a string or a string and a JSON pointer for inequality by converting the string to a
+   JSON pointer and comparing the JSON pointers according to 1.
+
+## Template parameters
+
+`RefStringTypeLhs`, `RefStringTypeRhs`
+:   the string type of the left-hand side or right-hand side JSON pointer, respectively
+
+`StringType`
+:   the string type derived from the `json_pointer` operand ([`json_pointer::string_t`](string_t.md))
+
+## Parameters
+
+`lhs` (in)
+:   first value to consider
+
+`rhs` (in)
+:   second value to consider
+
+## Return value
+
+whether the values `lhs`/`*this` and `rhs` are not equal
+
+## Exception safety
+
+1. No-throw guarantee: this function never throws exceptions.
+2. Strong exception safety: if an exception occurs, the original value stays intact.
+
+## Exceptions
+
+1. (none)
+2. The function can throw the following exceptions:
+   - Throws [parse_error.107](../../home/exceptions.md#jsonexceptionparse_error107) if the given JSON pointer `s` is
+     nonempty and does not begin with a slash (`/`); see example below.
+   - Throws [parse_error.108](../../home/exceptions.md#jsonexceptionparse_error108) if a tilde (`~`) in the given JSON
+     pointer `s` is not followed by `0` (representing `~`) or `1` (representing `/`); see example below.
+
+## Complexity
+
+Constant if `lhs` and `rhs` differ in the number of reference tokens, otherwise linear in the number of reference
+tokens.
+
+## Notes
+
+!!! note "Operator overload resolution"
+
+    Since C++20 overload resolution will consider the _rewritten candidate_ generated from
+    [`operator==`](operator_eq.md).
+
+## Examples
+
+??? example "Example: (1) Comparing JSON pointers"
+
+    The example demonstrates comparing JSON pointers.
+        
+    ```cpp
+    --8<-- "examples/json_pointer__operator__notequal.cpp"
+    ```
+    
+    Output:
+    
+    ```
+    --8<-- "examples/json_pointer__operator__notequal.output"
+    ```
+
+??? example "Example: (2) Comparing JSON pointers and strings"
+
+    The example demonstrates comparing JSON pointers and strings, and when doing so may raise an exception.
+        
+    ```cpp
+    --8<-- "examples/json_pointer__operator__notequal_stringtype.cpp"
+    ```
+    
+    Output:
+    
+    ```
+    --8<-- "examples/json_pointer__operator__notequal_stringtype.output"
+    ```
+
+## Version history
+
+1. Added in version 2.1.0.
+2. Added in version 3.11.2.

docs/mkdocs/mkdocs.yml

@@ -209,6 +209,8 @@ nav:
         - 'back': api/json_pointer/back.md
         - 'empty': api/json_pointer/empty.md
         - 'operator string_t': api/json_pointer/operator_string_t.md
+        - 'operator==': api/json_pointer/operator_eq.md
+        - 'operator!=': api/json_pointer/operator_ne.md
         - 'operator/': api/json_pointer/operator_slash.md
         - 'operator/=': api/json_pointer/operator_slasheq.md
         - 'parent_pointer': api/json_pointer/parent_pointer.md