Prev: FAQ 3.12 Where can I get perl-mode for emacs?
Next: Another bug - on 64-bit-integer-and-floatingpoint machines
From: PerlFAQ Server on 24 May 2010 12:00
This is an excerpt from the latest version perlfaq4.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

--------------------------------------------------------------------

4.8: How do I perform an operation on a series of integers?

To call a function on each element in an array, and collect the results,
use:

@results = map { my_func($_) } @array;

For example:

@triple = map { 3 * $_ } @single;

To call a function on each element of an array, but ignore the results:

foreach $iterator (@array) {
some_func($iterator);
}

To call a function on each integer in a (small) range, you can use:

@results = map { some_func($_) } (5 .. 25);

but you should be aware that the ".." operator creates an array of all
integers in the range. This can take a lot of memory for large ranges.
Instead use:

@results = ();
for ($i=5; $i < 500_005; $i++) {
push(@results, some_func($i));
}

This situation has been fixed in Perl5.005. Use of ".." in a "for" loop
will iterate over the range, without creating the entire range.

for my $i (5 .. 500_005) {
push(@results, some_func($i));
}

will not create a list of 500,000 integers.



--------------------------------------------------------------------

The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.

If you'd like to help maintain the perlfaq, see the details in
perlfaq.pod.
 | 
Pages: 1
Prev: FAQ 3.12 Where can I get perl-mode for emacs?
Next: Another bug - on 64-bit-integer-and-floatingpoint machines