protocol

geojson_protocol

GeoJSON (RFC 7946) parser, generator, and validator protocol.

Availability:
logtalk_load(geojson(loader))
Author: Paulo Moura
Version: 0:1:0
Date: 2026-05-08
Compilation flags:
static
Dependencies:
(none)
Remarks:
(none)
Inherited public predicates:
(none)

Public predicates

parse/2

Parses a GeoJSON document from the given source (file(Path), stream(Stream), codes(List), chars(List), or atom(Atom)) into a native GeoJSON term.

Compilation flags:
static
Template:
parse(Source,Term)
Mode and number of proofs:
parse(++compound,--term) - one_or_error
Exceptions:
Source is a variable:
instantiation_error
Source is neither a variable nor a valid source:
domain_error(geojson_source,Source)
Parsed JSON does not represent a valid GeoJSON document:
domain_error(geojson,Document)

generate/2

Generates GeoJSON content using the representation specified in the first argument (file(Path), stream(Stream), codes(List), chars(List), or atom(Atom)) from a native GeoJSON term.

Compilation flags:
static
Template:
generate(Sink,Term)
Mode and number of proofs:
generate(+compound,++term) - one_or_error
Exceptions:
Sink is a variable:
instantiation_error
Sink is neither a variable nor a valid sink:
domain_error(geojson_sink,Sink)
Term is not a valid GeoJSON term:
domain_error(geojson,Term)

validate/1

True iff the argument is a valid native GeoJSON term according to RFC 7946.

Compilation flags:
static
Template:
validate(Term)
Mode and number of proofs:
validate(@term) - zero_or_one

validate/2

Validates a native GeoJSON term returning a list of reason terms whose final argument is the failing path.

Compilation flags:
static
Template:
validate(Term,Errors)
Mode and number of proofs:
validate(@term,-list(compound)) - one_or_error
Remarks:

  • invalid_geojson_term(Path): The term is not any supported GeoJSON geometry, feature, or feature collection representation.

  • invalid_geometry(Path): A geometry member is neither a valid geometry term nor @null where @null is allowed.

  • invalid_properties(Path): A feature properties member is neither @null nor a valid JSON object term in the selected representation.

  • invalid_options(Path): The options argument is not a list.

  • option_not_allowed(Name, Path): An option with the given name is not allowed for the enclosing GeoJSON term.

  • duplicate_option(Name, Path): The same option name occurs more than once in the options list.

  • unknown_option(Option, Path): An option term is not recognized as one of the supported options.

  • invalid_bbox(Path): A bounding box is not a list of four or six numbers.

  • bbox_longitude_out_of_range(Path): A bounding box longitude value lies outside the RFC 7946 range [-180,180].

  • bbox_latitude_out_of_range(Path): A bounding box latitude value lies outside the RFC 7946 range [-90,90].

  • bbox_latitude_order(Path): The south latitude value is greater than the north latitude value in a bounding box.

  • bbox_altitude_order(Path): The minimum altitude value is greater than the maximum altitude value in a three-dimensional bounding box.

  • bbox_dimension_mismatch(Actual, Expected, Path): A bounding box length does not match the dimensionality required by the represented geometry, feature, or collection.

  • invalid_id(Path): A feature identifier is neither a number nor a valid string term in the selected representation.

  • invalid_foreign_members(Path): Foreign members are not represented as a valid pair list or embedded JSON object term, or contain an invalid pair term.

  • prohibited_member(Key, Path): A prohibited foreign member name such as crs was used.

  • reserved_foreign_member(Key, Path): A reserved GeoJSON member name was used as a foreign member key.

  • invalid_position(Path): A position is not a list of at least two numeric coordinates.

  • position_longitude_out_of_range(Path): A position longitude value lies outside the RFC 7946 range [-180,180].

  • position_latitude_out_of_range(Path): A position latitude value lies outside the RFC 7946 range [-90,90].

  • invalid_json_object_pair(Path): A JSON object member is not represented using a supported key-value pair term.

  • invalid_json_key(Path): A JSON object key is not a valid string term in the selected representation.

  • duplicate_json_object_key(Key, Path): The same JSON object key occurs more than once in the same object.

  • invalid_json_value(Path): A JSON value is not a number, boolean, null, valid string term, array, or object term.

  • insufficient_positions(MinimumLength, Path): A coordinate array contains fewer positions than required for the enclosing geometry.

  • invalid_position_array(Path): A coordinate array expected to contain positions is not a list of valid positions.

  • inconsistent_position_dimension(Path): Positions in the same coordinate array do not all have the same dimensionality.

  • invalid_line_string_array(Path): A MultiLineString coordinate array is not a valid list of line string coordinate arrays.

  • invalid_polygon(Path): A polygon coordinate structure is invalid, for example because it is not a non-empty list of linear rings.

  • ring_not_closed(Path): A linear ring does not repeat its first position as its last position.

  • invalid_multi_polygon(Path): A MultiPolygon coordinate array is not a valid list of polygon coordinate arrays.

  • invalid_geometry_collection(Path): A GeometryCollection geometries member is not a list.

  • invalid_feature_collection(Path): A FeatureCollection features member is not a list.

  • invalid_feature(Path): A value inside a FeatureCollection is not a valid feature term.

json_to_geojson/2

Converts a JSON term, as returned by the json library, into a native GeoJSON term.

Compilation flags:
static
Template:
json_to_geojson(JSON,GeoJSON)
Mode and number of proofs:
json_to_geojson(+term,-term) - one_or_error
Exceptions:
JSON is a variable:
instantiation_error
JSON is not a valid GeoJSON JSON term:
domain_error(geojson,JSON)

geojson_to_json/2

Converts a native GeoJSON term into a JSON term suitable for the json library.

Compilation flags:
static
Template:
geojson_to_json(GeoJSON,JSON)
Mode and number of proofs:
geojson_to_json(+term,-term) - one_or_error
Exceptions:
GeoJSON is a variable:
instantiation_error
GeoJSON is not a valid GeoJSON term:
domain_error(geojson,GeoJSON)

Protected predicates

(none)

Private predicates

(none)

Operators

(none)

See also

geojson, json, geospatial