Re: [Haskell-cafe] Ordered JSON objects?

On Wed, Dec 17, 2014 at 12:12:00PM +1300, Richard A. O'Keefe wrote:

On 16/12/2014, at 9:39 pm, Tobias Dammers wrote:

...

No, that's not what I meant. By "ordered", I meant that the in-memory representation of the document should maintain file order.

You did consult RFC 4627, right?

So if you depend on the order of the name/value pairs in a JSON object, you doing something surpassing strange and risky.

No need to go all RTFM on me; "JSON objects are unordered" is exactly what I was basing my reasoning on. I am not planning on depending on the order of something that is unordered by definition. However, my requirements are: 1. File format must be valid JSON (or occasionally YAML, or at least the JSON-isomorphic subset) 2. I need to represent ordered key/value collections 3. Conversion from JSON to the internal data type must be total (i.e., any valid JSON document must be accepted and converted to the most reasonable internal representation). Since JSON objects are (semantically) unordered, and the only way to get an ordered collection in JSON is through an array, my choices are: a) Use something that looks like JSON but defines objects as ordered key/value collections; this is something I *really* don't want, because it can break so many assumptions, and I would have to write my own JSON (and YAML) parsers for no good reason. b) Use an array of one-element objects. c) Use an array of keys and a key/value object side-by side. d) Use an array of objects, with a 'magic' property providing a tag name, and another magic property providing the payload value. e) Exactly like d), but gracefully accept other array elements, treating them as unnamed values. What I have implemented now is option e), with "_name" and "_value" for the magic properties; if neither is given, the element itself becomes an unnamed value, and can only be looked up by position; if a name is given but no value, it becomes a named null entry; if both are given, a proper name/value pair is generated. I'm still working out the details of if and what to throw away when an entry has both a "_value" and other properties, but other than that, I think this is as good as it gets. -- Tobias Dammers - tobias@twokings.nl - 070-3457628 - www.twokings.nl Maandag t/m donderdag van 9.00 tot 17.30 Voor dringende vragen, mail naar support@twokings.nl