Re: [stonehenge] deep copy what's the function getpwent()

They call those things iterators. An iterator is a function that returns items from a list until it runs out of them. When the list is exhausted, it returns a false value.

In Perl, they're usually written using a closure:

sub make_iterator {
    my (@list) = @_;

    return sub {
        # return a false value if exhausted
        return unless @list;

        # return next item in list
        return shift @list;
    };
}

my $iter = make_iterator(1..5);

while ( my $val = $iter->() ) {
    print $val, "\n";
}
[download]

Comment on Re: [stonehenge] deep copy what's the function getpwent() Download Code

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Re^2: [stonehenge] deep copy what's the function getpwent() by Anonymous Monk on Nov 29, 2013 at 07:53 UTC
Oh, and each is an iterator too. `while (($key, $value) = each %hash) { print $key, "\n"; }` [download] After "each" has returned all entries from the hash or array, the next call to "each" returns the empty list in list context and "undef" in scalar context. The next call following that one restarts iteration.	[reply] [d/l]

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Re^2: [stonehenge] deep copy what's the function getpwent()
by Anonymous Monk on Nov 29, 2013 at 07:53 UTC

each

while (($key, $value) = each %hash) {
    print $key, "\n";
}
[download]

               After "each" has returned all entries from the hash or array,
               the next call to "each" returns the empty list in list context
               and "undef" in scalar context.  The next call following that
               one restarts iteration.

[reply]
[d/l]