basic_json::operator==

bool operator==(const_reference lhs, const_reference rhs) noexcept;

template<typename ScalarType>
bool operator==(const_reference lhs, const ScalarType rhs) noexcept;

template<typename ScalarType>
bool operator==(ScalarType lhs, const const_reference rhs) noexcept;

Compares two JSON values for equality according to the following rules:

Two JSON values are equal if (1) they are from the same type and (2) their stored values are the same according to their respective operator==.
Integer and floating-point numbers are automatically converted before comparison. Note that two NaN values are always treated as unequal.
Two JSON null values are equal.

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 and rhs are equal

Exception safety

No-throw guarantee: this function never throws exceptions.

Complexity

Linear.

Notes

Floating-point inside JSON values numbers are compared with json::number_float_t::operator== which is double::operator== by default. To compare floating-point while respecting an epsilon, an alternative comparison function could be used, for instance

template<typename T, typename = typename std::enable_if<std::is_floating_point<T>::value, T>::type>
inline bool is_same(T a, T b, T epsilon = std::numeric_limits<T>::epsilon()) noexcept
{
    return std::abs(a - b) <= epsilon;
}

Or you can self-defined operator equal function like this:

bool my_equal(const_reference lhs, const_reference rhs)
{
    const auto lhs_type lhs.type();
    const auto rhs_type rhs.type();
    if (lhs_type == rhs_type)
    {
        switch(lhs_type)
            // self_defined case
            case value_t::number_float:
                return std::abs(lhs - rhs) <= std::numeric_limits<float>::epsilon();
            // other cases remain the same with the original
            ...
    }
...
}

NaN values never compare equal to themselves or to other NaN values.

Example

??? example

The example demonstrates comparing several JSON types.
    
```cpp
--8<-- "examples/operator__equal.cpp"
```

Output:

```json
--8<-- "examples/operator__equal.output"
```

Version history

Added in version 1.0.0.

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