package geojsone

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in-package search v0.2.0

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Maps
Folds
Iterators
Effect-based, non-blocking libraries

geojsone
- Geojsone
  - Err
  - Ezjsone
    
    List
  - G
    
    Accessor
    
    Feature
    
    Geometry
    
    Optics
    
    Either
    
    Infix
    
    Lens
    
    Optional
    
    Prism
    
    Feature
    
    Collection
    
    Geometry
    
    LineString
    
    MultiLineString
    
    MultiPoint
    
    MultiPolygon
    
    Point
    
    Polygon
    
    Position
    
    Random
  - Jsone
    
    Manual
    
    Uncut
  - Uutfe
    
    Buffer
    
    Manual
    
    String

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A library for manipulating large GeoJson documents without reading the whole document into memory using the Jsonm streaming, JSON parser.

module Err : sig ... end

module G : Geojson.S with type json = Ezjsone.value

Maps

Maps are functions that allow you to manipulate common structure in GeoJson objects. These will be written directly back to the destination that you provide.

val map_geometry : 
  (G.Geometry.t -> G.Geometry.t) ->
  Jsone.src ->
  Jsone.dst ->
  (unit, Err.t) result

map_geometry f src dst will apply f to all GeoJson objects. This is essentially any geometry object.

The map will recurse into geometry collections. Note for the moment if you have a single geometry object as your document, this will not work.

val map_props : 
  (Ezjsone.value -> Ezjsone.value) ->
  Jsone.src ->
  Jsone.dst ->
  (unit, Err.t) result

map_props src dst ~f will apply f to each feature's properties field. The properties field is decoded into an Ezjsone.value for convenience.

Folds

Folds are like maps except you can collect items into an accumulator which is returned to you.

For example, you might want to collect all of the names in the properties of features.

let get_string_exn = function `String s -> s | _ -> failwith "err"

let get_name = function
  | `O assoc -> List.assoc "name" assoc |> get_string_exn
  | _ -> failwith "err"

let places src =
  Geojsonm.fold_props (fun acc p -> get_name p :: acc) [] src

val fold_geometry : 
  ('a -> G.Geometry.t -> 'a) ->
  'a ->
  Jsone.src ->
  ('a, Err.t) result

fold_geometry f acc src is much like map_geometry but allows you to accumulate some result that is then returned to you.

val fold_props : 
  ('a -> Ezjsone.value -> 'a) ->
  'a ->
  Jsone.src ->
  ('a, Err.t) result

fold_props f init src

Iterators

Iterators are similar to map functions except they take a function f that takes a single element from the data-structure as an argument and returns unit. In that sense, they tend to be functions with side-effects, such as print_endline.

For example, we might want to print the JSON value of every geometry object in a GeoJSON object.

let print_geometry g =
  print_endline @@ Ezjsone.value_to_string (Geojsonm.G.Geometry.to_json g)

let values src = Geojsonm.iter_geometry print_geometry src

val iter_geometry : (G.t -> unit) -> Jsone.src -> (unit, Err.t) result

iter_geometry f src will apply f to all GeoJson objects.

val iter_props : (Ezjsone.value -> unit) -> Jsone.src -> (unit, Err.t) result

iter_props f src will apply f to each feature's properties field.

Effect-based, non-blocking libraries

These libraries use effects to perform non-blocking parsing. They are currently a part of Geojsone and exposed for other libraries to use.

module Ezjsone : sig ... end

module Jsone : sig ... end

module Uutfe : sig ... end