Ruby subsecond time addition incorrect

Question

I am having an issue with adding floating point numbers to time in ruby. In the example below, how is t2 not equal to 2013-02-15T01:17:17.996000000?

irb(main):094:0> t1.strftime("%Y-%m-%dT%H:%M:%S.%N")
=> "2013-02-15T01:16:47.785000000"
irb(main):095:0> t2 = t1 + 30.211
=> 2013-02-15 01:17:17 -0700
irb(main):096:0> t2.strftime("%Y-%m-%dT%H:%M:%S.%N")
=> "2013-02-15T01:17:17.995999999"

score 2 · Accepted Answer · answered Feb 20 '13 at 18:10

2

This is mainly about floating-point arithmetic.

Try 1.4 - 1.3 in the ruby shell.

What Every Computer Scientist Should Know About Floating-Point Arithmetic

answered Feb 20 '13 at 18:10

george.erickson

96
2

The answer is as correct as it's ever going to be. – tadman Feb 20 '13 at 18:18
Good article to explain, thanks. – dukebd711 Feb 20 '13 at 18:33

score 1 · Answer 2 · edited May 23 '17 at 11:49

1

This has been discussed before. You should check the following thread: ruby floating point errors

edited May 23 '17 at 11:49

Community

1
1

answered Feb 20 '13 at 18:15

lsu_guy

1,525
15
12

Ruby subsecond time addition incorrect

2 Answers2