From: Paul Eggert <eggert@cs.ucla.edu>
To: sds@gnu.org
Cc: emacs-devel@gnu.org
Subject: Re: inverse of float-time?
Date: Tue, 17 Sep 2013 14:10:22 -0700 [thread overview]
Message-ID: <5238C53E.6090102@cs.ucla.edu> (raw)
In-Reply-To: <87hadjdxm2.fsf@gnu.org>
On 09/17/13 13:03, Sam Steingold wrote:
> float-time should be either deprecated or granted equal rights :-)
It should be deprecated.
float-time is based on assumptions that go back to the Good
Old Days, when time stamps typically were 32-bit signed
integer counts of seconds, possibly with an additional
microseconds count. Under these assumptions float-time
doesn't lose information on typical platforms with IEEE
doubles, which are just barely large enough.
Nowadays, though, time_t is often 64 bits, and timestamps
are typically nanosecond resolution. IEEE doubles can't
represent these time stamps without losing information, so
float-time generates results with rounding errors.
If we could assume Guile, I suppose we could represent these modern
time stamps exactly, using fractions. That may be a good
way to go in the future. It'd be a lot more convenient than
the current list-of-integers representation.
> So, what is the official use case for float-time?
> When one would use it instead of time-date?
I assume that it was put in to make it convenient to compare
or subtract time stamps, or to add a time stamp to a seconds
count. (You added float-time back in 2000, so you should
know better than I. :-) These days, one should use
time-less-p, time-subtract, and time-add, as they shouldn't
have rounding errors.
next prev parent reply other threads:[~2013-09-17 21:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-11 17:39 inverse of float-time? Sam Steingold
2013-09-11 19:14 ` Paul Eggert
2013-09-11 19:31 ` Sam Steingold
2013-09-12 1:52 ` Leo Liu
2013-09-12 3:44 ` Sam Steingold
2013-09-12 4:16 ` Paul Eggert
2013-09-12 16:30 ` Ulrich Mueller
2013-09-17 20:03 ` Sam Steingold
2013-09-17 21:10 ` Paul Eggert [this message]
2013-09-12 3:07 ` SAKURAI Masashi
2013-09-12 3:42 ` Sam Steingold
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5238C53E.6090102@cs.ucla.edu \
--to=eggert@cs.ucla.edu \
--cc=emacs-devel@gnu.org \
--cc=sds@gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this external index
https://git.savannah.gnu.org/cgit/emacs.git
https://git.savannah.gnu.org/cgit/emacs/org-mode.git
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.