Niels Lohmann
a47170346a
* docs: new design for the documentation site Apply the brand to the Material for MkDocs site: Inter and JetBrains Mono served by the site (upright and real italic), brand colours, blue header band with the syntax pattern, wordmark in the header, new home page (hero, cards, animated feature tour), 404 page, polish for tabs, search, footer, focus rings, tables and code blocks, and theme features (code copy, previous/next footer, TOC follow, search suggestions). Draw the number railroad diagram, the parser callback events and the iterator illustrations as inline SVGs that follow the light and dark scheme. The generator scripts are in docs/mkdocs/scripts/figures; the feature slideshow (json-light.svg, json-dark.svg, replacing json.gif on the home page) is built by docs/mkdocs/scripts/slideshow. Decision nodes in five flowcharts become hexagons, which need far less room. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: add figures, table captions and a macro chooser - Figures with numbered captions: SAX stepper, json_view layout and edit stepper, exception map, JSON pointer and patch walkers, QA pipeline, scaling and binary size charts, roadmap lanes, release timeline, integration decision tree and namespace builder - Table captions (nj-table-caption) on 9 pages - Compile times: modules and PCH charts, filesystem section, re-measured Figure 1, links between features/modules.md and compile_times.md - Interactive macro chooser for features/arbitrary_types.md - Link check: exclude URLs that answer the plugin with 400/401/419 or are dead (customers.md) Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: macro chooser generates adl_serializer for non-default-constructible types Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: cross-link concept pages and API pages in See also sections Add See also links in both directions between the concept pages (features, home, integration) and the API pages, write API links in code font, give every entry a comment after a dash, and show the callback event figure on the parser callbacks page. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: address review comments on the new design - Home: add a "Latest release" button - Sponsors: update the list and group it by tier - Features: list all feature pages on the index page - Releases: add highlights per release, link the 4.0 roadmap, add the first commit to the timeline - Exceptions: prefix all example messages with the exception name - API: no code font for format names in the See also links of the to_/from_ pages - Merge Patch: show the document before, the patch, and the result - Replace "--" with typographic dashes, mark external links with an icon, center Mermaid diagrams Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>
3.5 KiB
3.5 KiB
nlohmann::basic_json::operator<=>
// since C++20
std::partial_ordering operator<=>(const_reference rhs) const noexcept; // (1)
template<typename ScalarType>
std::partial_ordering operator<=>(const ScalarType rhs) const noexcept(/* see below */); // (2)
-
3-way compares two JSON values producing a result of type
std::partial_orderingaccording to the following rules:- Two JSON values compare with a result of
std::partial_ordering::unorderedif either value is discarded. - If both JSON values are of the same type, the result is produced by 3-way comparing their stored values using
their respective
operator<=>. - Integer and floating-point numbers are 3-way compared by their exact values, without converting the integer to
floating-point. For instance,
9007199254740993compares greater than9007199254740992.0. - Otherwise, yields a result by comparing the type (see
value_t).
- Two JSON values compare with a result of
-
3-way compares a JSON value and a scalar or a scalar and a JSON value by converting the scalar to a JSON value and 3-way comparing both JSON values (see 1).
Template parameters
ScalarType- a scalar type according to
std::is_scalar<ScalarType>::value
Parameters
rhs(in)- second value to consider
Return value
the std::partial_ordering of the 3-way comparison of *this and rhs
Exception safety
- No-throw guarantee: this function never throws exceptions.
- No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
#!cpp nullptr; the function is#!cpp noexceptexactly in that case. Otherwise, it throws what the conversion throws, for examplestd::bad_allocwhen converting a string, orout_of_range.410for an enum value not mapped byNLOHMANN_JSON_SERIALIZE_ENUM_STRICT.
Complexity
Linear.
Notes
!!! note "Comparing NaN"
- `NaN` values are unordered within the domain of numbers.
The following comparisons all yield `std::partial_ordering::unordered`:
1. Comparing a `NaN` with itself.
2. Comparing a `NaN` with another `NaN`.
3. Comparing a `NaN` and any other number.
Examples
??? example "Example: (1) comparing JSON values"
The example demonstrates comparing several JSON values.
```cpp
--8<-- "examples/operator_spaceship__const_reference.c++20.cpp"
```
Output:
```json
--8<-- "examples/operator_spaceship__const_reference.c++20.output"
```
??? example "Example: (2) comparing JSON values and scalars"
The example demonstrates comparing several JSON values and scalars.
```cpp
--8<-- "examples/operator_spaceship__scalartype.c++20.cpp"
```
Output:
```json
--8<-- "examples/operator_spaceship__scalartype.c++20.output"
```
See also
operator==- comparison: equaloperator!=- comparison: not equaloperator<- comparison: less thanoperator<=- comparison: less than or equaloperator>- comparison: greater thanoperator>=- comparison: greater than or equal
Version history
- Added in version 3.11.0.
- Added in version 3.11.0.
Made conditionally
#!cpp noexceptin version 3.13.0; before, a throwing conversion calledstd::terminate.