.. _library_json_pointer:

`json_pointer`

The json_pointer library provides predicates for parsing, generating, and evaluating JSON Pointers as specified by RFC 6901, plus support for Relative JSON Pointer:

https://www.rfc-editor.org/rfc/rfc6901
https://json-schema.org/draft/2020-12/relative-json-pointer It supports both the plain string syntax and the URI fragment syntax for absolute JSON Pointers. Relative JSON Pointers use the plain string syntax. Reference tokens can be represented as atoms, chars(List), or codes(List).

API documentation

Open the `../../apis/library_index.html#json_pointer <../../apis/library_index.html#json_pointer>`__ link in a web browser.

Loading

To load all entities in this library, load the loader.lgt file:

| ?- logtalk_load(json_pointer(loader)).

Testing

To test this library predicates, load the tester.lgt file:

| ?- logtalk_load(json_pointer(tester)).

Representation

The library defines the json_pointer(_Representation_) parametric object where _Representation_ can be one of:

atom - reference tokens are represented as atoms
chars - reference tokens are represented as chars(List)
codes - reference tokens are represented as codes(List) When using the default json_pointer object, reference tokens are represented as atoms.
Relative JSON Pointer values are represented as relative(Up, Shift, Suffix):
Up is the number of ancestor steps
Shift is the optional signed array index adjustment
Suffix is either a list of reference tokens or the atom '#'

Examples

Parse and evaluate a pointer:

| ?- json_pointer::parse(atom('/foo/0'), Pointer), json_pointer::evaluate(Pointer, {foo-[bar, baz]}, Value). Pointer = [foo, '0'] Value = bar yes

Generate a URI fragment representation:

| ?- json_pointer::generate_fragment(atom(Fragment), ['a b', 'c/d']). Fragment = '#/a%20b/c~1d' yes

Evaluate a Relative JSON Pointer from a known context path:

| ?- json_pointer::evaluate_relative(relative(1, 0, ['0']), [foo, '1'], {foo-[bar, baz]}, Value). Value = bar yes