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Perl in a Nutshell, 2nd Edition
book

Perl in a Nutshell, 2nd Edition

by Nathan Patwardhan, Ellen Siever, Stephen Spainhour
June 2002
Beginner content levelBeginner
759 pages
80h 42m
English
O'Reilly Media, Inc.
Content preview from Perl in a Nutshell, 2nd Edition

sort

The sort pragma allows you to control sort() behavior. In Perl 5.6 and earlier, the default sort() behavior was written with quicksort. Perl 5.8, with which sort.pm is shipped in the source kit, implements mergesort. mergesort guarantees the worst-case behavior of O(N log N), where quicksort guarantees O(N ** 2).

Perl 5.8 and later shuffle large arrays before sorting. Note that sort.pm is global and not lexical in scope.

For example:

#!/usr/local/bin/perl -w
use sort '_quicksort'; # Or _qsort, if you'd like
sort(@something);

mergesort is better than quicksort for several reasons. First, mergesort is more stable and does fewer comparisons than quicksort, so it’s better for more complicated sorting routines. In addition, mergesort takes preexisting order into account.

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Publisher Resources

ISBN: 0596002416Errata Page