[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: inverse of float-time?
From: |
Paul Eggert |
Subject: |
Re: inverse of float-time? |
Date: |
Tue, 17 Sep 2013 14:10:22 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130805 Thunderbird/17.0.8 |
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.
- inverse of float-time?, Sam Steingold, 2013/09/11
- Re: inverse of float-time?, Paul Eggert, 2013/09/11
- Re: inverse of float-time?, Sam Steingold, 2013/09/11
- Re: inverse of float-time?, Leo Liu, 2013/09/11
- Re: inverse of float-time?, Sam Steingold, 2013/09/11
- Re: inverse of float-time?, Paul Eggert, 2013/09/12
- Re: inverse of float-time?, Ulrich Mueller, 2013/09/12
- Re: inverse of float-time?, Sam Steingold, 2013/09/17
- Re: inverse of float-time?,
Paul Eggert <=
Re: inverse of float-time?, SAKURAI Masashi, 2013/09/11