6b97599a27
* Add C++20 3-way comparison operator and fix broken comparisons Fixes #3207. Fixes #3409. * Fix iterators to meet (more) std::ranges requirements Fixes #3130. Related discussion: #3408 * Add note about CMake standard version selection to unit tests Document how CMake chooses which C++ standard version to use when building tests. * Update documentation * CI: add legacy discarded value comparison * Fix internal linkage errors when building a module
2.5 KiB
2.5 KiB
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)
};
-
Compares two JSON values for inequality according to the following rules:
- The comparison always yields
#!cpp falseif (1) either operand is discarded, or (2) either operand isNaNand the other operand is eitherNaNor any other number. - Otherwise, returns the result of
#!cpp !(lhs == rhs)(until C++20) or#!cpp !(*this == rhs)(since C++20).
- The comparison always yields
-
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
!!! note "Comparing NaN"
`NaN` values are unordered within the domain of numbers.
The following comparisons all yield `#!cpp false`:
1. Comparing a `NaN` with itself.
2. Comparing a `NaN` with another `NaN`.
3. Comparing a `NaN` and any other number.
Examples
??? example
The example demonstrates comparing several JSON types.
```cpp
--8<-- "examples/operator__notequal.cpp"
```
Output:
```json
--8<-- "examples/operator__notequal.output"
```
??? example
The example demonstrates comparing several JSON types against the null pointer (JSON `#!json null`).
```cpp
--8<-- "examples/operator__notequal__nullptr_t.cpp"
```
Output:
```json
--8<-- "examples/operator__notequal__nullptr_t.output"
```
Version history
- Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
- Added in version 1.0.0. Added C++20 member functions in version 3.11.0.