Subject: Re: bug#55163: 29.0.50; master 4a1f69ebca (TICKS . HZ) for current-time broke lsp-mode

From: Paul Eggert <[email-masked]>
Date: Sun, 1 May 2022 08:00:05 -0700

On 4/30/22 22:38, Eli Zaretskii wrote:
>> it's common for Emacs to compare the timestamp of a file at
>> time T1 with the timestamp of another (or the same) file at a later
>> time T2.

> Please show at least 3 examples of such "common" situations.  I think
> it is rather UN-common.

auth-source-netrc-parse, semanticdb-synchronize, and dir-locals-find-file.

> what's the problem to describe and support a primitive that
> returns a sorted list of files?

What happens with ties in the timestamps - do we sort stably? What 
happens with files named but not present? What if we want to sort by 
ctime instead of by mtime? What if the user is involved in selecting 
files as we go? How do we specify the files: a list of strings, a 
pattern, or something else? What if we want to look at a tree of files? Etc.

Of course one could come up with answers to those questions, but this 
sort of thing is much better handled in Lisp code than as a C-language 
primitive.

> I challenge you to present even half a dozen of such uses.

I listed three examples above. Here are three more, which makes six: 
multisession-backend-value, eshell-read-passwd, 
nneething-create-mapping. More examples can easily be supplied.

>> There are also cases where the code now uses current-time and assumes
>> that the resulting timestamps are issued in numeric order, an assumption
>> that is not always true in practice.
> 
> That's a separate issue, and again: please present the use cases for
> that which are relevant to Emacs applications.

erc-server-send-ping, progress-reporter-do-update, timer-event-handler. 
I'm sure there are others.

Your point is well taken that if we made changes along the lines being 
discussed, we shouldn't merely add the new primitives: we should *use* 
them. And if we can't find significant use for them then we shouldn't 
add them.