json_basic.fn

// Typed JSON: parse text into a JsonValue, read fields with typed accessors, and
// render back with stringify.

imp std.c.io;
imp std.json;
imp std.result;

fun main() num {
  let src = "{\"name\": \"fun\", \"version\": 1, \"stable\": true}";

  fit parse(src) {
    Result.Ok(doc) -> {
      // get(key) returns Option<JsonValue>; the as_* accessors narrow the type.
      let name = doc.get("name").unwrap_or(JsonValue.Null);
      printf("name=%s\n", name.as_str().unwrap_or("?"));

      let version = doc.get("version").unwrap_or(JsonValue.Null);
      printf("version=%g\n", version.as_num().unwrap_or(0.0));

      // Round-trips back to JSON text.
      printf("json=%s\n", doc.to_string());
    }
    Result.Err(e) -> { printf("parse failed\n"); }
  }

  ret 0;
}