JSON

Json is a host-backed standard-library extern datatype. Programs construct and inspect it through the Json module rather than relying on JavaScript object representation.

Construct JSON values

The module provides constructors for every JSON shape:

func document() -> Json do
  Json.object([
    ("name", Json.string("Noodle")),
    ("count", Json.int(3)),
    ("active", Json.bool(true)),
    ("tags", Json.array([Json.string("typed"), Json.string("modular")])),
    ("extra", Json.null()),
  ])
end

Json.number accepts Double; Json.int preserves the convenient explicit integer boundary. Object entries are supplied as an array of (String, Json) tuples.

Parse and stringify

Json.parse(text) returns Result[Json, String]; the error string describes invalid JSON input. Json.stringify(value) returns compact JSON text:

func normalize(text : String) -> Result[String, String] do
  switch Json.parse(text)
  case Result::Ok(value) then Result::Ok(Json.stringify(value))
  case Result::Err(message) then Result::Err(message)
  end
end

This example handles the Result explicitly. A throws wrapper can propagate a declared error type when the application wants a domain-specific failure contract.

Inspect directly through Json

Json is an extern datatype with six constructors: Null plus five @unboxed single-positional payloads (Bool, Num, Str, Arr, Obj). Matching classifies the host value with the recognize_json companion and binds the scrutinee value itself — no wrapper is allocated:

func describe(value : Json) -> String do
  switch value
  case Json::Null then "null"
  case Json::Bool(flag) then flag.to_string()
  case Json::Num(number) then number.to_string()
  case Json::Str(text) then text
  case Json::Arr(items) then
    "array(" ++ items.length().to_string() ++ ")"
  case Json::Obj(object) then
    "object(" ++ object.entries().length().to_string() ++ ")"
  end
end

JsonObject.field(name) returns Option[Json]; entries() returns the object’s entries as an array.

Next: Output, debugging, and tests.