P is for Practical PerlMonks

### Comment on

 Need Help??
While investigating Benchmark.pm I decided to try benchmarking different sorting algorithms, and have run into trouble with my implementation of <dfn>Merge Sort</dfn>;
```sub Merge(@) {
my @array = @_;
MergeSort (0, \$#array);
return @array;

sub MergeSort(\$\$) {
my \$first = shift;
my \$last = shift;
if (\$last>\$first) {
my \$mid = int((\$last+\$first)/2);
MergeSort(\$first, \$mid);
MergeSort(\$mid+1, \$last);
my @b;

@b = ( @array[\$first..\$mid], @array[reverse(\$mid+1..\$last)] );
my (\$i, \$j, \$k) = (0, \$last-\$first, \$first);
for (; \$k<=\$last; \$k++) {
\$array[\$k] = (\$b[\$i]<\$b[\$j]) ? \$b[\$i++] : \$b[\$j--];
}
}
}
}
The function works perfectly, but with warnings turned on, spits out the following:
```Variable "@array" will not stay shared at ./benchmark-sort.pl line [x]
+.
Where [x] is the first line in MergeSort() which manipulates @array.

Presumably I'm doing something naive here to do with the scoping of @array, which, in slightly different circumstances, could cause errors rather than just warnings.

So, what does the warning mean, and how should I declare @array to avoid it?

In reply to Scoped Variables in a Recursive Function. by kilinrax

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

• Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
• Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
• Read Where should I post X? if you're not absolutely sure you're posting in the right place.
• Posts may use any of the Perl Monks Approved HTML tags:
a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
• You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
 For: Use: & & < < > > [ [ ] ]
• Link using PerlMonks shortcuts! What shortcuts can I use for linking?

Create A New User
Chatterbox?
NodeReaper files his shovel

How do I use this? | Other CB clients
Other Users?
Others exploiting the Monastery: (2)
As of 2017-08-22 04:17 GMT
Sections?
Information?
Find Nodes?
Leftovers?
Voting Booth?
Who is your favorite scientist and why?

Results (328 votes). Check out past polls.

Notices?