[Rd] RFC: System and time support functions in R
Prof Brian Ripley
Prof Brian Ripley <email@example.com>
Thu, 20 Jul 2000 14:33:51 +0100 (BST)
> From: Martin Maechler <firstname.lastname@example.org>
> Date: Thu, 20 Jul 2000 15:24:33 +0200 (CEST)
> To: Prof Brian Ripley <email@example.com>
> BDR> ISO C (aka ANSI C) has time_t, but no guarantee that it is seconds
> BDR> 1/1/1970. POSIX in general tightens up the definitions considerably.
> Most you probably know this, .. but
> since there's the "unix millenium bug" aka "C millenium bug",
> POSIX or it's successor will have to extend/change the definition of time_t
> to use 64bit integers (or something else) instead of (32-bit) long int as
> it is now, since time will overflow some time in 2038 (?).
> Our structure should make sure to accomodate more than only about 2^31
> seconds since 1970-Jan-01.
Nothing in POSIX that I know of says time_t has to be an signed 32-bit int,
and some systems use long (64-bit) or double or long double already,
my book says. There is already a problem with 32-bit ints in only
going back to the early years of this century.
This is an argument against making use of the system conversion
functions for a chron replacement, and I think that what I called
POSIXtm (an list) is a more general format.
> chron() even now uses double which should be okay, even if we'd go down to
> parts of seconds -- something we might consider.
I intended to use double in R to store time_t. (Yes, I know file.info
does not currently, but what is there is a place holder.)
> How are financial "tick data" recorded nowadays (and in five years from now)
To one second, those that I have used.
Brian D. Ripley, firstname.lastname@example.org
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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