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| author | John P. Linderman <jpl@research.att.com> | 2003-07-10 06:45:06 -0400 |
|---|---|---|
| committer | Rafael Garcia-Suarez <rgarciasuarez@gmail.com> | 2003-07-11 19:37:34 +0000 |
| commit | 0319020171ad67607dd7a06e238d6c91ff7d4639 (patch) | |
| tree | 19402c153de30b39d89708b176ec6e6daf1dfab0 /pod | |
| parent | b49f3be6643e5cc849effc933e4e4e100d534a4e (diff) | |
| download | perl-0319020171ad67607dd7a06e238d6c91ff7d4639.tar.gz | |
Re: Sort sub and NaNs
From: "John P. Linderman" <jpl@research.att.com>
Message-Id: <200307101445.KAA79110@raptor.research.att.com>
Warn against a potential edge case with sort, <=> and NaNs.
p4raw-id: //depot/perl@20156
Diffstat (limited to 'pod')
| -rw-r--r-- | pod/perlfunc.pod | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod index 3686736fcf..612b9cdd70 100644 --- a/pod/perlfunc.pod +++ b/pod/perlfunc.pod @@ -4758,6 +4758,15 @@ inconsistent results (sometimes saying C<$x[1]> is less than C<$x[2]> and sometimes saying the opposite, for example) the results are not well-defined. +Because C<< <=> >> returns C<undef> when either operand is C<NaN> +(not-a-number), and because C<sort> will trigger a fatal error unless the +result of a comparison is defined, when sorting with a comparison function +like C<< $a <=> $b >>, be careful about lists that might contain a C<NaN>. +The following example takes advantage of the fact that C<NaN != NaN> to +eliminate any C<NaN>s from the input. + + @result = sort { $a <=> $b } grep { $_ == $_ } @input; + =item splice ARRAY,OFFSET,LENGTH,LIST =item splice ARRAY,OFFSET,LENGTH |