a=Time.now;(Time.parse(a.to_s)-a)!=0

Ruby
1

Hmm. Ooh yuck.

Try this…

$ ruby -r time -e ‘a=Time.now;p a-Time.parse(a.to_s)’
0.00848
$ ruby -r time -e ‘a=Time.now;p a-Time.parse(a.to_s)’
0.446575
$ ruby -r time -e ‘a=Time.now;p a-Time.parse(a.to_s)’
0.142796

ie. Time#to_s doesn’t represent the full precision of the internal
time format.

Bit of a bummer if you want to round trip an exact timestamp onto disk
and back.

This does it right…
$ ruby -e ‘a=Time.now;p a-Marshal::load(Marshal::dump(a))’
0.0

…but look at whats on disk…
ruby -e ‘a=Time.now;p Marshal::dump(a)’
“\004\bu:\tTime\rC\347\032\200z\343S\302”

Eeew! Not exactly human friendly.

The following is probably the most elegant way of exactly round
tripping a time to disk and back in a human readable form?

ruby -w -rtime -e ‘a=Time.now;b = a.xmlschema(6);p b;p
a-Time.xmlschema(b)’
“2007-10-26T17:01:08.129059+13:00”
0.0

Ah well.

John C. Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : [email protected]
New Zealand

2

On 26 Oct 2007, at 13:03, John C. wrote:

Time.xmlschema(b)’
“2007-10-26T17:01:08.129059+13:00”
0.0

You can use YAML if you only want Time.

irb(main):002:0> Time.now.to_yaml
=> “— 2007-10-26 13:10:45.012414 +09:00\n”
irb(main):003:0> YAML.load(Time.now.to_yaml)
=> Fri Oct 26 13:10:55 +0900 2007

irb(main):004:0> t = Time.now
=> Fri Oct 26 13:13:05 +0900 2007
irb(main):005:0> t - YAML.load(t.to_yaml)
=> 0.0

Though there’s a bug with DateTime:

irb(main):006:0> DateTime.now.to_yaml
=> “— !timestamp 2007-10-26T13:11:15+0900\n”
irb(main):007:0> YAML.load(DateTime.now.to_yaml)
=> Wed Sep 19 10:11:26 +0900 2007

Alex G.

Bioinformatics Center
Kyoto University

3

John C. a écrit :

a-Time.xmlschema(b)’

Hi,
It seems that Time objects are precise to the microsecond, but to_s (and
to_i) limit the precision to one second.

a= Time.now
b = Time.parse(a.to_s)
a-b #=> 0.875
a.usec #=> 875000

I guess you could get a full representation of a Time object by
combining to_s (or to_i) with #usec

4

On Oct 25, 2007, at 10:03 PM, John C. wrote:

ruby -w -rtime -e ‘a=Time.now;b = a.xmlschema(6);p b;p a-
Time.xmlschema(b)’
“2007-10-26T17:01:08.129059+13:00”
0.0

though i prefer #iso8601 to #xmlschema because even typing the word
‘xml’ makes my skin crawl :wink:

a @ http://codeforpeople.com/