Skip to content

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)
  1. Compares whether one JSON value lhs is greater than another JSON value rhs 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) (see operator<=).
  2. Compares wether a JSON value is greater than a scalar or a scalar is greater than a JSON value 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 lhs is greater than rhs

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. 2. Comparing a NaN with another NaN. 3. Comparing a NaN and any other number.

Operator overload resolution

Since C++20 overload resolution will consider the rewritten candidate generated from operator<=>.

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 = 17.0000000000001L;
    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] false
{"A":"a","B":"b"} > {"A":"a","B":"b"} false
17 > 17.0000000000001 false
"foo" > "bar" true

See also

Version history

  1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
  2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.

Last update: September 18, 2022