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* [Bug c++/47706] New: std::min/max and NaN
@ 2011-02-11 20:15 dieter.lucking at googlemail dot com
2011-02-12 1:55 ` [Bug c++/47706] " paolo.carlini at oracle dot com
2011-02-12 6:27 ` paolo.carlini at oracle dot com
0 siblings, 2 replies; 3+ messages in thread
From: dieter.lucking at googlemail dot com @ 2011-02-11 20:15 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47706
Summary: std::min/max and NaN
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: dieter.lucking@googlemail.com
This seems to be a contradiction:
((0.0 < std::numeric_limits<double>::quiet_NaN()) ? 0.0 :
std::numeric_limits<double>::quiet_NaN()) => `nan'
std::min(0.0, std::numeric_limits<double>::quiet_NaN()) => `0'
^ permalink raw reply [flat|nested] 3+ messages in thread* [Bug c++/47706] std::min/max and NaN 2011-02-11 20:15 [Bug c++/47706] New: std::min/max and NaN dieter.lucking at googlemail dot com @ 2011-02-12 1:55 ` paolo.carlini at oracle dot com 2011-02-12 6:27 ` paolo.carlini at oracle dot com 1 sibling, 0 replies; 3+ messages in thread From: paolo.carlini at oracle dot com @ 2011-02-12 1:55 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47706 Paolo Carlini <paolo.carlini at oracle dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution| |INVALID --- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-02-12 01:38:07 UTC --- There is nothing to fix here. I suppose you agree that any comparison involving NaNs is false, thus you first example is ok. The second one invokes undefined behavior, because among the requirements of std::min is that the type T must be LessThanComparable and when you instantiate std::min with a floating point T including NaNs in its domain the '<' isn't irreflexive. ^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/47706] std::min/max and NaN 2011-02-11 20:15 [Bug c++/47706] New: std::min/max and NaN dieter.lucking at googlemail dot com 2011-02-12 1:55 ` [Bug c++/47706] " paolo.carlini at oracle dot com @ 2011-02-12 6:27 ` paolo.carlini at oracle dot com 1 sibling, 0 replies; 3+ messages in thread From: paolo.carlini at oracle dot com @ 2011-02-12 6:27 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47706 --- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-02-12 01:54:53 UTC --- Never mind the second half of my comment, the issue has nothing to do with irreflexivity of course. The point is, in the implementation of std::min the comparison fails and the first argument is returned, because the standard wants the first argument if the arguments are equivalent. Given the latter requirement + only LessThanComparable is required, I don't see how the behavior could be different. ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2011-02-12 1:55 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2011-02-11 20:15 [Bug c++/47706] New: std::min/max and NaN dieter.lucking at googlemail dot com 2011-02-12 1:55 ` [Bug c++/47706] " paolo.carlini at oracle dot com 2011-02-12 6:27 ` paolo.carlini at oracle dot com
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