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Diffstat (limited to 'chromium/third_party/cygwin/lib/perl5/5.10/sort.pm')
| -rw-r--r-- | chromium/third_party/cygwin/lib/perl5/5.10/sort.pm | 196 |
1 files changed, 0 insertions, 196 deletions
diff --git a/chromium/third_party/cygwin/lib/perl5/5.10/sort.pm b/chromium/third_party/cygwin/lib/perl5/5.10/sort.pm deleted file mode 100644 index 922f82b4691..00000000000 --- a/chromium/third_party/cygwin/lib/perl5/5.10/sort.pm +++ /dev/null @@ -1,196 +0,0 @@ -package sort; - -our $VERSION = '2.01'; - -# 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; - -use strict; - -sub import { - shift; - if (@_ == 0) { - require Carp; - Carp::croak("sort pragma requires arguments"); - } - 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') { - $^H{sort} |= $sort::stable_bit; - } elsif ($_ eq 'defaults') { - $^H{sort} = 0; - } else { - require Carp; - Carp::croak("sort: unknown subpragma '$_'"); - } - } -} - -sub unimport { - shift; - if (@_ == 0) { - require Carp; - Carp::croak("sort pragma requires arguments"); - } - 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') { - $^H{sort} &= ~$sort::stable_bit; - } else { - require Carp; - Carp::croak("sort: unknown subpragma '$_'"); - } - } -} - -sub current { - my @sort; - if ($^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); -} - -1; -__END__ - -=head1 NAME - -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 { - $current = sort::current(); # identify prevailing algorithm - } - -=head1 DESCRIPTION - -With the C<sort> pragma you can control the behaviour of the builtin -C<sort()> function. - -In Perl versions 5.6 and earlier the quicksort algorithm was used to -implement C<sort()>, but in Perl 5.8 a mergesort algorithm was also made -available, mainly to guarantee worst case O(N log N) behaviour: -the worst case of quicksort is O(N**2). In Perl 5.8 and later, -quicksort defends against quadratic behaviour by shuffling large -arrays before sorting. - -A stable sort means that for records that compare equal, the original -input ordering is preserved. Mergesort is stable, quicksort is not. -Stability will matter only if elements that compare equal can be -distinguished in some other way. That means that simple numerical -and lexical sorts do not profit from stability, since equal elements -are indistinguishable. However, with a comparison such as - - { substr($a, 0, 3) cmp substr($b, 0, 3) } - -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 -say so with a - - use sort 'stable'; - -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"; - -have exactly the same effect, leaving the choice of sort algorithm open. - -=head1 CAVEATS - -As of Perl 5.10, this pragma is lexically scoped and takes effect -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 - print sort::current . "\n"; - @a = sort @b; - eval 'use sort "defaults"'; # clean up, for others - } - { eval 'use sort qw(defaults stable)'; # force stability - print sort::current . "\n"; - @c = sort @d; - eval 'use sort "defaults"'; # clean up, for others - } - -Such code no longer has the desired effect, for two reasons. -Firstly, the use of C<eval()> means that the sorting algorithm -is not changed until runtime, by which time it's too late to -have any effect. Secondly, C<sort::current> is also called at -run-time, when in fact the compile-time value of C<sort::current> -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 - my $current; - BEGIN { $current = print sort::current; } - print "$current\n"; - @a = sort @b; - # Pragmas go out of scope at the end of the block - } - { use sort qw(defaults stable); # force stability - my $current; - BEGIN { $current = print sort::current; } - print "$current\n"; - @c = sort @d; - } - -=cut - |