nlohmann::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 whether one JSON value lhs
is less than another JSON value rhs
according to the following rules:
- If
lhs
andrhs
have the same type, the values are compared using the default<
operator. - Integer and floating-point numbers are automatically converted before comparison
- Discarded values a
-
In case
lhs
andrhs
have different types, the values are ignored and the order of the types is considered, which is:- null
- boolean
- number (all types)
- object
- array
- string
- binary
For instance, any boolean value is considered less than any string.
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 less than rhs
Exception safety¶
No-throw guarantee: this function never throws exceptions.
Complexity¶
Linear.
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] true
{"A":"a","B":"b"} == {"A":"a","B":"b"} false
17 == 17.0000000000001 true
"foo" == "bar" false
Version history¶
- Added in version 1.0.0.
Last update: May 1, 2022