RE: [odata] Reference for types of collections

["Handl, Ralf" <ralf.handl@sap.com>]

https://www.stefanjudis.com/today-i-learned/property-order-is-predictable-in-_javascript_-objects-since-es2015/

 

Modern _javascript_ retains insert order of object keys except for integer indices: these appear first in the overall object property order and are sorted numerically.

 

Still some way to goâ

 

From: odata@lists.oasis-open.org <odata@lists.oasis-open.org> On Behalf Of Stefan Hagen
Sent: Thursday, 9 February 2023 20:53
To: Ericson, George <George.Ericson@dell.com>; Theissen, Heiko <heiko.theissen@sap.com>
Cc: odata@lists.oasis-open.org
Subject: Re: [odata] Reference for types of collections

 

Short comment from the side lines,

 

order is an overloaded term for many ... and hashing is hard.

 

Maybe not so important and even fuzzy thoughts:

 

- Python has ordered (insert order) collections (tuple, list) and

  sets (set, frozenset, dict) built in.

- Sorted (dynamically maintained sorted order) containers are

  third-party contributions for python.

- C++ std unfortunately introduces confusion by mixing up

  (actively) sorted containers with (insert) ordered containers.

  Esp. the abundant map is sorting by element domain attribute.

- I write this, because advocating stable insert ordering would

  offer much more streamable JSON objects when the serializing

  and deserializing host components could rely on containers

  with insert order ... that could also spare the decorative Rococo

  of embedding JSON objects inside JSON arrays only to fixate

  the order not because there are no unique keys available.

- Python 3.6 introduced the stable insert order and in addition

  delivered a performance boost which provided magic like

  a cake we can eat and keep too.

 

I still hope for RFC 987654321 providing such a revised JSON.

 

All the best,

Stefan

 

On Wed, Feb 8, 2023, at 22:47, Ericson, George wrote:

Here is the reference mentioned today in our discussion on types of collections.

https://www.omg.org/spec/OCL/2.4/PDF.  See sections 11.6 and following.

 

My summary of the definitions from the OCL reference.

OCL	Description
collection	an aggregation of elements. If an element occurs twice in a collection, there are two elements.
set	contains elements without duplicates.
orderedset	a set, the elements of which are ordered. It contains no duplicates.
bag	a collection with duplicates allowed.
sequence	a collection where the elements are ordered.

 

My comparison between C++ and OCL terms.

C++	~OCL	C++ Description
container	collection	An object that stores other objects.
unordered_map unordered_set	set	an unordered associative container that supports unique keys (an unordered_set contains at most one of each key value) and in which the elementsâ keys are the elements themselves.
map set	orderedset	an ordered associative container that supports unique keys (contains at most one of each key value) and provides for fast retrieval of the keys themselves.
unordered_multimap unordered_multiset	bag	an unordered associative container that supports equivalent keys (an instance of unordered_multiset may contain multiple copies of the same key value) and in which each elementâs key is the element itself.
multimap multiset	sequence	an ordered associative container that supports equivalent keys (possibly contains multiple copies of the same key value) and provides for fast retrieval of the keys themselves.

 

Thanks,

George

 

 

Stefan Hagen, Emmetten, Nidwalden, Switzerland.

orcid: https://orcid.org/0000-0003-4206-892X

read: https://stefan-hagen.website

write: stefan@hagen.link