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authorKarl Berry <karl@freefriends.org>2019-03-10 21:56:14 +0000
committerKarl Berry <karl@freefriends.org>2019-03-10 21:56:14 +0000
commite0a2a718e89f9700d627f1e6a8eea8f21d2fbeb8 (patch)
tree39972f65008b0d70f306a5f976494d29411bc41e /Master/tlpkg/tlperl/lib/sort.pm
parentb206fdc77d81ed1600949062f08de5690a4bf66f (diff)
tl19 perl 5.28.1 for Windows, from Siep
git-svn-id: svn://tug.org/texlive/trunk@50322 c570f23f-e606-0410-a88d-b1316a301751
Diffstat (limited to 'Master/tlpkg/tlperl/lib/sort.pm')
-rw-r--r--Master/tlpkg/tlperl/lib/sort.pm76
1 files changed, 16 insertions, 60 deletions
diff --git a/Master/tlpkg/tlperl/lib/sort.pm b/Master/tlpkg/tlperl/lib/sort.pm
index 7c8e50db577..659f3e4f4d8 100644
--- a/Master/tlpkg/tlperl/lib/sort.pm
+++ b/Master/tlpkg/tlperl/lib/sort.pm
@@ -1,14 +1,12 @@
package sort;
-our $VERSION = '2.02';
+our $VERSION = '2.04';
# The hints for pp_sort are now stored in $^H{sort}; older versions
# of perl used the global variable $sort::hints. -- rjh 2005-12-19
-$sort::quicksort_bit = 0x00000001;
-$sort::mergesort_bit = 0x00000002;
-$sort::sort_bits = 0x000000FF; # allow 256 different ones
$sort::stable_bit = 0x00000100;
+$sort::unstable_bit = 0x00000200;
use strict;
@@ -21,14 +19,9 @@ sub import {
local $_;
$^H{sort} //= 0;
while ($_ = shift(@_)) {
- if (/^_q(?:uick)?sort$/) {
- $^H{sort} &= ~$sort::sort_bits;
- $^H{sort} |= $sort::quicksort_bit;
- } elsif ($_ eq '_mergesort') {
- $^H{sort} &= ~$sort::sort_bits;
- $^H{sort} |= $sort::mergesort_bit;
- } elsif ($_ eq 'stable') {
+ if ($_ eq 'stable') {
$^H{sort} |= $sort::stable_bit;
+ $^H{sort} &= ~$sort::unstable_bit;
} elsif ($_ eq 'defaults') {
$^H{sort} = 0;
} else {
@@ -47,12 +40,9 @@ sub unimport {
local $_;
no warnings 'uninitialized'; # bitops would warn
while ($_ = shift(@_)) {
- if (/^_q(?:uick)?sort$/) {
- $^H{sort} &= ~$sort::sort_bits;
- } elsif ($_ eq '_mergesort') {
- $^H{sort} &= ~$sort::sort_bits;
- } elsif ($_ eq 'stable') {
+ if ($_ eq 'stable') {
$^H{sort} &= ~$sort::stable_bit;
+ $^H{sort} |= $sort::unstable_bit;
} else {
require Carp;
Carp::croak("sort: unknown subpragma '$_'");
@@ -63,11 +53,8 @@ sub unimport {
sub current {
my @sort;
if ($^H{sort}) {
- push @sort, 'quicksort' if $^H{sort} & $sort::quicksort_bit;
- push @sort, 'mergesort' if $^H{sort} & $sort::mergesort_bit;
push @sort, 'stable' if $^H{sort} & $sort::stable_bit;
}
- push @sort, 'mergesort' unless @sort;
join(' ', @sort);
}
@@ -81,16 +68,12 @@ sort - perl pragma to control sort() behaviour
=head1 SYNOPSIS
use sort 'stable'; # guarantee stability
- use sort '_quicksort'; # use a quicksort algorithm
- use sort '_mergesort'; # use a mergesort algorithm
use sort 'defaults'; # revert to default behavior
no sort 'stable'; # stability not important
- use sort '_qsort'; # alias for quicksort
-
my $current;
BEGIN {
- $current = sort::current(); # identify prevailing algorithm
+ $current = sort::current(); # identify prevailing pragmata
}
=head1 DESCRIPTION
@@ -98,15 +81,8 @@ sort - perl pragma to control sort() behaviour
With the C<sort> pragma you can control the behaviour of the builtin
C<sort()> function.
-In Perl versions 5.6 and earlier the quicksort algorithm was used to
-implement C<sort()>, but in Perl 5.8 a mergesort algorithm was also made
-available, mainly to guarantee worst case O(N log N) behaviour:
-the worst case of quicksort is O(N**2). In Perl 5.8 and later,
-quicksort defends against quadratic behaviour by shuffling large
-arrays before sorting.
-
A stable sort means that for records that compare equal, the original
-input ordering is preserved. Mergesort is stable, quicksort is not.
+input ordering is preserved.
Stability will matter only if elements that compare equal can be
distinguished in some other way. That means that simple numerical
and lexical sorts do not profit from stability, since equal elements
@@ -116,22 +92,10 @@ are indistinguishable. However, with a comparison such as
stability might matter because elements that compare equal on the
first 3 characters may be distinguished based on subsequent characters.
-In Perl 5.8 and later, quicksort can be stabilized, but doing so will
-add overhead, so it should only be done if it matters.
-
-The best algorithm depends on many things. On average, mergesort
-does fewer comparisons than quicksort, so it may be better when
-complicated comparison routines are used. Mergesort also takes
-advantage of pre-existing order, so it would be favored for using
-C<sort()> to merge several sorted arrays. On the other hand, quicksort
-is often faster for small arrays, and on arrays of a few distinct
-values, repeated many times. You can force the
-choice of algorithm with this pragma, but this feels heavy-handed,
-so the subpragmas beginning with a C<_> may not persist beyond Perl 5.8.
-The default algorithm is mergesort, which will be stable even if
-you do not explicitly demand it.
-But the stability of the default sort is a side-effect that could
-change in later versions. If stability is important, be sure to
+
+Whether sorting is stable by default is an accident of implementation
+that can change (and has changed) between Perl versions.
+If stability is important, be sure to
say so with a
use sort 'stable';
@@ -139,15 +103,9 @@ say so with a
The C<no sort> pragma doesn't
I<forbid> what follows, it just leaves the choice open. Thus, after
- no sort qw(_mergesort stable);
-
-a mergesort, which happens to be stable, will be employed anyway.
-Note that
-
- no sort "_quicksort";
- no sort "_mergesort";
+ no sort 'stable';
-have exactly the same effect, leaving the choice of sort algorithm open.
+sorting may happen to be stable anyway.
=head1 CAVEATS
@@ -156,8 +114,7 @@ at compile time. In earlier versions its effect was global and took
effect at run-time; the documentation suggested using C<eval()> to
change the behaviour:
- { eval 'use sort qw(defaults _quicksort)'; # force quicksort
- eval 'no sort "stable"'; # stability not wanted
+ { eval 'no sort "stable"'; # stability not wanted
print sort::current . "\n";
@a = sort @b;
eval 'use sort "defaults"'; # clean up, for others
@@ -177,8 +134,7 @@ is the one that matters.
So now this code would be written:
- { use sort qw(defaults _quicksort); # force quicksort
- no sort "stable"; # stability not wanted
+ { no sort "stable"; # stability not wanted
my $current;
BEGIN { $current = sort::current; }
print "$current\n";