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Niels Lohmann a47170346a docs: new design for the documentation site (#5934 )

* 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>

2026-10-27 07:41:42 +01:00

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nlohmann::json_pointer

template<typename RefStringType>
class json_pointer;

A JSON pointer defines a string syntax for identifying a specific value within a JSON document. It can be used with functions at and operator[]. Furthermore, JSON pointers are the base for JSON patches.

Template parameters

RefStringType: the string type used for the reference tokens making up the JSON pointer

!!! warning "Deprecation"

For backwards compatibility `RefStringType` may also be a specialization of [`basic_json`](../basic_json/index.md)
in which case `string_t` will be deduced as [`basic_json::string_t`](../basic_json/string_t.md). This feature is
deprecated and may be removed in a future major version.

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

A JSON pointer is internally a sequence of reference tokens. front, pop_front, and push_front act on the first reference token, whereas back, pop_back, and push_back act on the last one. parent_pointer returns a new JSON pointer with the last reference token removed (like a non-mutating pop_back):

flowchart LR
    A["a"] --> B["b"] --> C["c"]

    front["front() / pop_front() / push_front()"] -.-> A
    back["back() / pop_back() / push_back()"] -.-> C
    parent["parent_pointer() returns /a/b"] -.-> B

Boxes are the reference tokens in order; dotted arrows show which token each member function reads, removes, or adds to.

The diagram shows the reference tokens of the JSON pointer /a/b/c.

Member types

string_t - the string type used for the reference tokens

Member functions

(constructor)
to_string - return a string representation of the JSON pointer
operator string_t - return a string representation of the JSON pointer (deprecated)
operator== - compare: equal
operator!= - compare: not equal
operator<=> - compare: 3-way (C++20)
operator/= - append to the end of the JSON pointer
operator/ - create JSON Pointer by appending
parent_pointer - returns the parent of this JSON pointer
pop_back - remove the last reference token
back - return last reference token
push_back - append an unescaped token at the end of the pointer
pop_front - remove the first reference token
front - return first reference token
push_front - append an unescaped token at the start of the pointer
empty - return whether the pointer points to the root document

Literals

operator""_json_pointer - user-defined string literal for JSON pointers

Version history

Added in version 2.0.0.
Changed template parameter from basic_json to string type in version 3.11.0.

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