FAQ 4.7: How do I perform an operation on a series of integers?

This message is one of several periodic postings to DevShed's Perl forum intended to make it easier for Perl programmers to find answers to common questions. The core of this message represents an excerpt from the documentation provided with every Standard Distribution of Perl.

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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.
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