nlohmann::json_pointer::operator<=>

// since C++20
class json_pointer {
    template<typename RefStringTypeRhs>
    std::strong_ordering operator<=>(const json_pointer<RefStringTypeRhs>& rhs) const noexcept; // *NOPAD*
};

3-way compares two JSON pointers by lexicographically comparing their sequences of reference tokens: corresponding reference tokens are compared with string_t's own operator<=>, and the first pair of tokens that differs determines the result. If all corresponding reference tokens compare equal, the JSON pointer with fewer reference tokens is ordered first.

Template parameters

RefStringTypeRhs: the string type of the right-hand side JSON pointer

Parameters

rhs (in): JSON pointer to compare *this with

Return value

the std::strong_ordering of the 3-way comparison of *this and rhs

Exception safety

No-throw guarantee: this function never throws exceptions.

Complexity

Linear in the number of reference tokens.

Notes

!!! note "Ordering enables use as an associative container key"

Together with [`operator==`](operator_eq.md), `operator<=>` makes `json_pointer` a `LessThanComparable` type, so
it can be used as the key type of ordered associative containers such as `std::map` or `std::set`.

!!! note "Before C++20"

Without C++20's three-way comparison, `json_pointer` provides a non-member `operator<` instead, which orders JSON
pointers the same way. JSON pointers can therefore be used as keys of ordered associative containers with any
supported C++ standard.

Examples

??? example

The example demonstrates 3-way comparing JSON pointers.

```cpp
--8<-- "examples/json_pointer__operator_spaceship.c++20.cpp"
```

Output:

```
--8<-- "examples/json_pointer__operator_spaceship.c++20.output"
```

Version history

Added in version 3.11.2.

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