Re: sqlite3

[LdBeth]

On Sat, 18 Dec 2021 15:53:04 +0800,
Qiantan Hong wrote:
> 
> Therefore I conclude that maybe preserving EQness in persistent store
> does not make that much sense (otherwise why it can only be preserved
> partially?).
> 
> I do see practical usefulness of partial EQness preservation.


It seems no one has yet pointed out "preserving EQness" is actually
hash-consing[1], a technique has been developed in Lisp and now well
known in Functional Programming communities.

It has main features that:

1. Keeps only one copy of (structurally) EQUAL objects and therefore
2. reduce storage usage
3. reduce the time needed to do a EQUAL comparsion to EQ.
4. useful for function memoization

It is definitely useful, but I think we could make it into a separated
package, probably.

[1]: A. .P. Ershov. On Programming of Arithmetic Operations. In the
Communications of the ACM, Volume 118, Number 3, August, 1958, pages
427–430.