# \[Bug:trunk\] rubyspec: Time#+ rounds micro seconds rather than truncates FAILED

**URL:** <https://www.ruby-forum.com/t/bug-trunk-rubyspec-time-rounds-micro-seconds-rather-than-truncates-failed/183253>\
**Category:** Development\
**Created:** [February 10, 2010, 6:59pm UTC](https://www.ruby-forum.com/t/bug-trunk-rubyspec-time-rounds-micro-seconds-rather-than-truncates-failed/183253 "2010-02-10T18:59:11Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [February 10, 2010, 6:59pm UTC](https://www.ruby-forum.com/t/bug-trunk-rubyspec-time-rounds-micro-seconds-rather-than-truncates-failed/183253/1 "2010-02-10T18:59:11Z")

</div>

akr e$B$5$se(B  
e$B1sF#$G$9!#e(B

Evan P. e$B$He(B Time e$B$N5sF0$K$D$$$FAjCL$7$?\>e$Ge(B Time  
e$B$K$D$$$F0l1~$Ne(B  
e$B3NG’$G$9!#e(B

- 1.8 e$B$Ne(B Time#+ e$B$Oe(B usec e$B$G;M\<N8^F~$7$F$$$^$9$,!“e(B1.9  
e$B$G$O$7$^$;$s!#e(B  
e$BFbItI=8=$,e(B Rational  
e$B$K$J$C$?$N$@$+$iEvA3$@$H;W$$$^$9$,!”;EMMJQ99e(B  
e$B$G$9$h$M!#e(B

- 1.8 e$B$Ne(B Time#usec e$B$de(B nsec  
e$B$,;M\<N8^F~$7$J$$$N$O;EMM$G$9$h$M!#e(B  
usec e$B$,e(B 1000000 e$B$H$+$K$J$C$?$i7y$G$9$b$N$M!#e(B

e$B$=$&$@$h$s$H8@$C$F$/$@$5$l$P!"0J2\<$N%3%_%C%H$re(B rubyspec  
e$B$K%3%_%C%He(B  
e$B$7$h$&$H;W$$$^$9!#e(B

diff --git a/core/time/plus\_spec.rb b/core/time/plus\_spec.rb  
index 1f5c85f…e333430 100644  
— a/core/time/plus\_spec.rb  
+++ b/core/time/plus\_spec.rb  
@@ -10,21 +10,33 @@ describe “Time#+” do  
(Time.at(1.1) + 0.9).should == Time.at(0.9) + 1.1  
end

- it “rounds micro seconds rather than truncates” do
- 
# The use of 8.9999999 is intentional. This is because
- 
# Time treats the fractional part as the number of micro seconds.
- 
# Thusly it multiplies the result by 1\_000\_000 to go from
- 
# seconds to microseconds. That conversion should be rounded
- 
# properly. In this case, it’s rounded up to 1,000,000, and thus
- 
# contributes a full extra second to the Time object.
- t = Time.at(0) + 8.9999999
- t.should == Time.at(9)
- t.usec.should == 0

- ruby\_version\_is “” … “1.9” do
- it “rounds micro seconds rather than truncates” do
- 

```
 # The use of 8.9999999 is intentional. This is because

```

- 

```
 # Time treats the fractional part as the number of micro seconds.

```

- 

```
 # Thusly it multiplies the result by 1_000_000 to go from

```

- 

```
 # seconds to microseconds. That conversion should be rounded

```

- 

```
 # properly. In this case, it's rounded up to 1,000,000, and thus

```

- 

```
 # contributes a full extra second to the Time object.

```

- 

```
 t = Time.at(0) + 8.9999999

```

- 

```
 t.should == Time.at(9)

```

- 

```
 t.usec.should == 0

```

- 
- 

```
 # Check the non-edge case works properly, that the fractional 

```

part

- 

```
 # contributes to #usecs

```

- 

```
 t2 = Time.at(0) + 8.9

```

- 

```
 t2.usec.should == 900000

```

- end
- end

- 
# Check the non-edge case works properly, that the fractional part
- 
# contributes to #usecs
- t2 = Time.at(0) + 8.9
- t2.usec.should == 900000

- ruby\_version\_is “1.9” do
- it “does NOT round” do
- 

```
 t = Time.at(0) + Rational(8_999_999_999_999_999, 

```

1\_000\_000\_000\_000\_000)

- 

```
 t.should_not == Time.at(9)

```

- 

```
 t.usec.should == 999_999

```

- 

```
 t.nsec.should == 999_999_999

```

- 

```
 t.subsec.should == Rational(999_999_999_999_999, 

```

1\_000\_000\_000\_000\_000)

- end  
end

ruby\_version\_is “” … “1.9” do

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [February 11, 2010, 1:37pm UTC](https://www.ruby-forum.com/t/bug-trunk-rubyspec-time-rounds-micro-seconds-rather-than-truncates-failed/183253/2 "2010-02-11T13:37:13Z")

</div>

2010e$BG/e(B2e$B7ne(B11e$BF|e(B2:58 Yusuke ENDOH [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> - 1.8 e$B$Ne(B Time#+ e$B$Oe(B usec e$B$G;M\<N8^F~$7$F$$$^$9$,!“e(B1.9 e$B$G$O$7$^$;$s!#e(B  
> e$BFbItI=8=$,e(B Rational e$B$K$J$C$?$N$@$+$iEvA3$@$H;W$$$^$9$,!”;EMMJQ99e(B  
> e$B$G$9$h$M!#e(B

1.9.2 e$B$G$O$=$&$G$9!#e(B  
1.9.1 e$B$NFbItI=8=$Oe(B nsec e$BC10L$J$N$G!"e(Bnsec  
e$B$G;M\<N8^F~$J$s$G$O$J$$$+$H;W$$$^$9!#e(B

> - 1.8 e$B$Ne(B Time#usec e$B$de(B nsec e$B$,;M\<N8^F~$7$J$$$N$O;EMM$G$9$h$M!#e(B  
> usec e$B$,e(B 1000000 e$B$H$+$K$J$C$?$i7y$G$9$b$N$M!#e(B

1.8 e$B$Ke(B nsec  
e$B$O$“$j$^$;$s$,!”$^$!$=$&$J$i$6$k$rF@$J$$$G$9$+$M!#e(B

e$B7+$j\>e$,$k@h$,$"$k\>l9g$O$I$&$+$J$!!#e(B

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [February 11, 2010, 1:59pm UTC](https://www.ruby-forum.com/t/bug-trunk-rubyspec-time-rounds-micro-seconds-rather-than-truncates-failed/183253/3 "2010-02-11T13:59:28Z")

</div>

e$B1sF#$G$9!#e(B

2010e$BG/e(B2e$B7ne(B11e$BF|e(B21:36 Tanaka A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> > usec e$B$,e(B 1000000 e$B$H$+$K$J$C$?$i7y$G$9$b$N$M!#e(B
> 
> 1.8 e$B$Ke(B nsec e$B$O$“$j$^$;$s$,!”$^$!$=$&$J$i$6$k$rF@$J$$$G$9$+$M!#e(B

e$B$"$j$,$H$&$4$6$$$^$9!#%3%\_%C%H$5$;$FD:$-$^$7$?!#e(B

e$B$A$J$_$Ke(B rubyspec e$B$Oe(B 1.9.1  
e$B$N;EMM$rL5;k$9$kJ}?K$i$7$$$G$9e(B (1.9.1 e$B$He(B  
1.9.2 e$B$N4V$G;EMMJQ99$,$"$j$9$.$@$+$ie(B) e$B!#$J$N$G!“e(B1.9  
e$B$H=q$$$F$”$l$Pe(B  
1.9.2 e$B0J9_$r;X$9$H$$$&$3$H$G$9!#e(B

> e$B7+$j\>e$,$k@h$,$"$k\>l9g$O$I$&$+$J$!!#e(B

e$B8D?ME\*$K$O@Z$j\<N$F$,$o$+$j$d$9$$$N$G$=$l$G$$$$$H;W$$$^$9$,!"JQ$($ke(B  
e$B$J$iJQ$($F$b$i$C$F$b9=$o$J$$$G$9!#e(Brubyspec e$BB&$r=$@5$7$^$9!#e(B

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [February 11, 2010, 3:02pm UTC](https://www.ruby-forum.com/t/bug-trunk-rubyspec-time-rounds-micro-seconds-rather-than-truncates-failed/183253/4 "2010-02-11T15:02:07Z")

</div>

> > 個人的には切り捨てがわかりやすいのでそれでいいと思いますが、変える  
> > なら変えてもらっても構わないです。rubyspec 側を修正します。
> 
> 仕掛けがわかりやすいからといって結果がわかりやすいかというと  
> 微妙なのではないかと。
> 
> 切り捨てで処理するのは崖っぷちを歩くようなもので、  
> ひとつ間違えると意図せざる結果になりがちです。
> 
> とりあえず Time#round(ndigits) とかどうかなぁ。

Timeの元データは何があるんでしょう？一番苦情がくるのは oldtime \> newtime または oldtime \> now  
になってしまうケースで、oldtimeが精度落とすときに切り上げされていてnowが高精度だったりすると  
起こせそうな気がします。

個人的には切り捨てに一票で、理由は「え、思ってたよりちょっと古い時刻だった？そりゃ測定してるうちにも時間は  
経過するからねHAHAHA」でほとんどのケースは済んでしまうコーナーケースの少なさに利点があるかと。

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [February 11, 2010, 2:50pm UTC](https://www.ruby-forum.com/t/bug-trunk-rubyspec-time-rounds-micro-seconds-rather-than-truncates-failed/183253/5 "2010-02-11T14:50:24Z")

</div>

2010e$BG/e(B2e$B7ne(B11e$BF|e(B21:58 Yusuke ENDOH [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> e$B8D?ME\*$K$O@Z$j\<N$F$,$o$+$j$d$9$$$N$G$=$l$G$$$$$H;W$$$^$9$,!"JQ$($ke(B  
> e$B$J$iJQ$($F$b$i$C$F$b9=$o$J$$$G$9!#e(Brubyspec e$BB&$r=$@5$7$^$9!#e(B

e$B;E3]$1$,$o$+$j$d$9$$$+$i$H$$$C$F7k2L$,$o$+$j$d$9$$$+$H$$$&$He(B  
e$BHyL/$J$N$G$O$J$$$+$H!#e(B

e$B@Z$j\<N$F$G=hM}$9$k$N$O33$C$W$A$rJb$/$h$&$J$b$N$G!"e(B  
e$B$R$H$D4V0c$($k$H0U?^$;$6$k7k2L$K$J$j$,$A$G$9!#e(B

e$B$H$j$"$($:e(B Time#round(ndigits) e$B$H$+$I$&$+$J$!!#e(B

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [February 11, 2010, 4:16pm UTC](https://www.ruby-forum.com/t/bug-trunk-rubyspec-time-rounds-micro-seconds-rather-than-truncates-failed/183253/6 "2010-02-11T16:16:28Z")

</div>

2010e$BG/e(B2e$B7ne(B11e$BF|e(B23:01 KOSAKI Motohiro  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> Timee$B$N85%G!\<%?$O2?$,$"$k$s$G$7$g$&!)0lHV6l\>p$,$/$k$N$Oe(B oldtime \> newtime e$B$^$?$Oe(B oldtime \> now  
> e$B$K$J$C$F$7$^$&%1!\<%9$G!"e(Boldtimee$B$,@:EYMn$H$9$H$-$K@Z$j\>e$2$5$l$F$$$Fe(Bnowe$B$,9b@:EY$@$C$?$j$9$k$He(B  
> e$B5/$3$;$=$&$J5$$,$7$^$9!#e(B

e$B$9$0$K;W$$=P$;$k$N$Oe(B

- e$B8=:\_;~9oe(B  
gettimeofday e$B$N%^%$%/%mICe(B  
clock\_gettime e$B$N%J%NICe(B
- e$B%U%!%$%k$N%?%$%`%9%?%s%We(B  
st\_mtime e$B$J$I$NICe(B  
st\_mtim e$B$J$I$N%J%NICe(B
- e$B%Q%1%C%H$N%?%$%`%9%?%s%We(B  
SCM\_TIMESTAMP e$B$N%^%$%/%mICe(B  
SCM\_TIMESTAMPNS e$B$N%J%NICe(B  
SCM\_BINTIME e$B$Ne(B 2\*\*(-64)e$BICe(B
- Ruby e$BFbe(B  
DateTime e$B$NM-M}?te(B
- e$B3F\<o%U%)!\<%^%C%He(B  
ISO 8601 e$B$Oe(B10e$B?J?t$G\>.?tE@0J2\<G$0U7eICe(B  
e$B$/$i$$$+$J$!!#e(B

e$B$I$l$b@53N$Ke(B Time e$B$KJQ49$G$-$^$9!#e(B  
e$B$^$!!"e(BTime e$B$NCf?H$Oe(B (e$B35G0E\*$K$Oe(B) e$BM-M}?t$J$s$G!#e(B

> e$B8D?ME\*$K$O@Z$j\<N$F$K0lI\<$G!“M}M3$O!V$(!”;W$C$F$?$h$j$A$g$C$H8E$$;~9o$@$C$?!)$=$j$cB,Dj$7$F$k$&$A$K$b;~4V$Oe(B  
> e$B7P2a$9$k$+$i$Me(BHAHAHAe$B!W$G$[$H$s$I$N%1!\<%9$O:Q$s$G$7$^$&%3!\<%J!\<%1!\<%9$N\>/$J$5$KMxE@$,$"$k$+$H!#e(B

e$B$J$k$[$I!#e(B

e$B$^$!!"$=$N$&$Ae(B

% ./ruby -ve ’  
t = Time.new(1989,3,3)  
p t, t + 0.3 + 0.7’  
ruby 1.9.2dev (2010-02-11 trunk 26640) [i686-linux]  
1989-03-03 00:00:00 +0900  
1989-03-03 00:00:00 +0900

e$B$,JQ$@$H8@$$=P$9$R$H$,=P$F$/$k$s$8$c$J$$$+$J$!!"$H$$$&$/$i$$$NOC$J$N$G!“e(B  
e$B8=\<BE\*$K@Z$j\<N$F$KMxE@$,B?$$$J$i%G%U%)%k%H$=$C$A$H$$$&$N$O$”$j$&$ke(B  
e$BA\*Br;h$+$J$!!#e(B

e$B$=$l$O4]$a$?$$$H$-$K;H$($k%a%=%C%I$,$"$k$3$H$H$OL7=b$7$^$;$s$,!#e(B

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [April 20, 2010, 1:39pm UTC](https://www.ruby-forum.com/t/bug-trunk-rubyspec-time-rounds-micro-seconds-rather-than-truncates-failed/183253/7 "2010-04-20T13:39:53Z")

</div>

e$B%A%1%C%He(B #2733 e$B$,99?7$5$l$^$7$?!#e(B (by Yusuke E.)

e$B%9%F!\<%?%9e(B Assignede$B$+$ie(BRejectede$B$KJQ99e(B

e$B1sF#$G$9!#e(B

e$B2r7h:Q$\_$J$N$Ge(B close e$B$7$^$9!#e(B

## – Yusuke E. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

[http://redmine.ruby-lang.org/issues/show/2733](http://redmine.ruby-lang.org/issues/show/2733)