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[p5sagit/p5-mst-13.2.git] / lib / sort.pm

diff --git a/lib/sort.pm b/lib/sort.pm
index 18f3606..3db4777 100644 (file)
--- a/lib/sort.pm
+++ b/lib/sort.pm
@@ -1,8 +1,13 @@
 package sort;
 
-our $VERSION = '1.00';
+our $VERSION = '1.01';
 
-$sort::hint_bits       = 0x00020000; # HINT_LOCALIZE_HH, really...
+# Currently the hints for pp_sort are stored in the global variable
+# $sort::hints. An improvement would be to store them in $^H{SORT} and have
+# this information available somewhere in the listop OP_SORT, to allow lexical
+# scoping of this pragma. -- rgs 2002-04-30
+
+our $hints            = 0;
 
 $sort::quicksort_bit   = 0x00000001;
 $sort::mergesort_bit   = 0x00000002;
@@ -17,18 +22,17 @@ sub import {
        require Carp;
        Carp::croak("sort pragma requires arguments");
     }
-    $^H |= $sort::hint_bits;
     local $_;
-    no warnings 'uninitialized';       # $^H{SORT} bitops would warn
+    no warnings 'uninitialized';       # bitops would warn
     while ($_ = shift(@_)) {
        if (/^_q(?:uick)?sort$/) {
-           $^H{SORT} &= ~$sort::sort_bits;
-           $^H{SORT} |=  $sort::quicksort_bit;
+           $hints &= ~$sort::sort_bits;
+           $hints |=  $sort::quicksort_bit;
        } elsif ($_ eq '_mergesort') {
-           $^H{SORT} &= ~$sort::sort_bits;
-           $^H{SORT} |=  $sort::mergesort_bit;
+           $hints &= ~$sort::sort_bits;
+           $hints |=  $sort::mergesort_bit;
        } elsif ($_ eq 'stable') {
-           $^H{SORT} |=  $sort::stable_bit;
+           $hints |=  $sort::stable_bit;
        } else {
            require Carp;
            Carp::croak("sort: unknown subpragma '$_'");
@@ -38,10 +42,10 @@ sub import {
 
 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} & $sort::stable_bit;
+    if ($hints) {
+       push @sort, 'quicksort' if $hints & $sort::quicksort_bit;
+       push @sort, 'mergesort' if $hints & $sort::mergesort_bit;
+       push @sort, 'stable'    if $hints & $sort::stable_bit;
     }
     push @sort, 'mergesort' unless @sort;
     join(' ', @sort);
@@ -77,7 +81,7 @@ 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.  Perl's mergesort is stable, quicksort is not.
+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
@@ -100,5 +104,10 @@ caches that are much faster than main memory.  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.
 
+=head1 CAVEATS
+
+This pragma is not lexically scoped : its effect is global to the program
+it appears in.  This may change in future versions.
+
 =cut