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>
2.2 KiB
nlohmann::basic_json_view::back
basic_json_view back() const;
Returns the last element of an array, the last member value of an object, or the value itself if it is primitive
(as for BasicJsonType::back(), a primitive value is a range of one element).
Return value
The last element or member value. For a primitive value (number, string, boolean), the value itself.
Exception safety
Strong guarantee: there are no changes to the view or the document it refers to.
Exceptions
Throws invalid_iterator.214 if the view is
null or discarded, or if it is an empty array or object.
This exception does not carry a JSON_DIAGNOSTICS path: the view has no
BasicJsonType value to point at, so the exception is created without one, even if BasicJsonType was built with
JSON_DIAGNOSTICS enabled.
Complexity
Linear in the size of the array or object: unlike front(), which only ever looks at the first
element, back() has to walk every element to find where they end, since elements are not a fixed size in the
index. Constant if no element of the array is an array or object, since the elements are then adjacent
in the index.
Notes
Unlike BasicJsonType::back(), which has undefined behavior for an empty array or object,
back() throws invalid_iterator.214 for an empty array, an empty object, a null value, or a discarded view.
Examples
??? example
The example below reads only the final status of a build log with `back()`. Even though `back()` is linear in
the number of events (unlike [`front()`](front.md), which is constant), it still avoids building a
`BasicJsonType` value for the events that are not needed.
```cpp
--8<-- "examples/basic_json_view__back.cpp"
```
Output:
```json
--8<-- "examples/basic_json_view__back.output"
```
See also
front- access the first elementBasicJsonType::back- the corresponding function ofbasic_json
Version history
- Added in version 3.13.0.