json/api/basic_json/operator_ge.md

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(/* see below */); // (2)

template<typename ScalarType>
bool operator>=(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)

1. Compares whether one JSON value lhs is greater than or equal to another JSON value rhs according to the following rules:

   • The comparison always yields #!cpp 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 #!cpp !(lhs < rhs) (see operator<).

2. Compares whether a JSON value is greater than or equal to a scalar or a scalar is greater than or equal to 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 or equal to rhs

Exception safety

1. No-throw guarantee: this function never throws exceptions.
2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and #!cpp nullptr; the function is #!cpp noexcept exactly in that case. Otherwise, it throws what the conversion throws, for example std::bad_alloc when converting a string, or out_of_range.410 for an enum value not mapped by NLOHMANN_JSON_SERIALIZE_ENUM_STRICT.

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.

!!! note "Operator overload resolution"

Since C++20 overload resolution will consider the _rewritten candidate_ generated from
[`operator<=>`](operator_spaceship.md).

!!! warning "Deprecation"

If [`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](../macros/json_use_legacy_discarded_value_comparison.md) is
defined to `1`, the library declares a member `#!cpp bool operator>=(const_reference rhs) const noexcept` in
C++20 mode to emulate the legacy comparison of discarded values. This member is deprecated since version 3.11.0,
together with the legacy comparison behavior.

See the [migration guide](../../integration/migration_guide.md#miscellaneous-functions) for how to update existing
code.

Examples

??? example

The example demonstrates comparing several JSON types.
    
```cpp
#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:

```json
[1,2,3] >= [1,2,4] false
{"A":"a","B":"b"} >= {"A":"a","B":"b"} true
17 >= 17.0000000000001 false
"foo" >= "bar" true

```

See also

• operator<=> comparison: 3-way

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. Made conditionally #!cpp noexcept in version 3.13.0; before, a throwing conversion called std::terminate.