deploy: 7c9208bfb3

api/basic_json/operator_ne/index.md

@@ -0,0 +1,145 @@
+# nlohmann::basic_json::operator!=
+
+```
+// until C++20
+bool operator!=(const_reference lhs, const_reference rhs) noexcept;   // (1)
+
+template<typename ScalarType>
+bool operator!=(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+
+template<typename ScalarType>
+bool operator!=(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+
+// since C++20
+class basic_json {
+    bool operator!=(const_reference rhs) const noexcept;              // (1)
+
+    template<typename ScalarType>
+    bool operator!=(ScalarType rhs) const noexcept;                   // (2)
+};
+```
+
+1. Compares two JSON values for inequality according to the following rules:
+
+   - The comparison always yields `false` if (1) either operand is discarded, or (2) either operand is `NaN` and the other operand is either `NaN` or any other number.
+   - Otherwise, returns the result of `!(lhs == rhs)` (until C++20) or `!(*this == rhs)` (since C++20).
+
+1. Compares a JSON value and a scalar or a scalar and a JSON value for inequality by converting the scalar to a JSON value and comparing both JSON values according to 1.
+
+## Template parameters
+
+`ScalarType` : a scalar type according to `std::is_scalar<ScalarType>::value`
+
+## 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
+
+No-throw guarantee: this function never throws exceptions.
+
+## Complexity
+
+Linear.
+
+## Notes
+
+Comparing `NaN`
+
+`NaN` values are unordered within the domain of numbers. The following comparisons all yield `false`:
+
+1. Comparing a `NaN` with itself.
+1. Comparing a `NaN` with another `NaN`.
+1. Comparing a `NaN` and any other number.
+
+## Examples
+
+Example
+
+The example demonstrates comparing several JSON types.
+
+```
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create several JSON values
+    json array_1 = {1, 2, 3};
+    json array_2 = {1, 2, 4};
+    json object_1 = {{"A", "a"}, {"B", "b"}};
+    json object_2 = {{"B", "b"}, {"A", "a"}};
+    json number_1 = 17;
+    json number_2 = 17.000000000000001L;
+    json string_1 = "foo";
+    json string_2 = "bar";
+
+    // output values and comparisons
+    std::cout << std::boolalpha;
+    std::cout << array_1 << " != " << array_2 << " " << (array_1 != array_2) << '\n';
+    std::cout << object_1 << " != " << object_2 << " " << (object_1 != object_2) << '\n';
+    std::cout << number_1 << " != " << number_2 << " " << (number_1 != number_2) << '\n';
+    std::cout << string_1 << " != " << string_2 << " " << (string_1 != string_2) << '\n';
+}
+```
+
+Output:
+
+```
+[1,2,3] != [1,2,4] true
+{"A":"a","B":"b"} != {"A":"a","B":"b"} false
+17 != 17.0 false
+"foo" != "bar" true
+```
+
+Example
+
+The example demonstrates comparing several JSON types against the null pointer (JSON `null`).
+
+```
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create several JSON values
+    json array = {1, 2, 3};
+    json object = {{"A", "a"}, {"B", "b"}};
+    json number = 17;
+    json string = "foo";
+    json null;
+
+    // output values and comparisons
+    std::cout << std::boolalpha;
+    std::cout << array << " != nullptr " << (array != nullptr) << '\n';
+    std::cout << object << " != nullptr " << (object != nullptr) << '\n';
+    std::cout << number << " != nullptr " << (number != nullptr) << '\n';
+    std::cout << string << " != nullptr " << (string != nullptr) << '\n';
+    std::cout << null << " != nullptr " << (null != nullptr) << '\n';
+}
+```
+
+Output:
+
+```
+[1,2,3] != nullptr true
+{"A":"a","B":"b"} != nullptr true
+17 != nullptr true
+"foo" != nullptr true
+null != nullptr false
+```
+
+## Version history
+
+1. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
+1. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.