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lib/Algorithm/Loops.pm  view on Meta::CPAN

        my @copy= Filter( sub {s/\s/_/g}, @list );

=head3 Note on "Function BLOCK LIST" bugs

Note that in at least some versions of Perl, support for the "Filter
BLOCK ..." syntax is somewhat fragile.  For example:

    ... Filter( {y/aeiou/UAEIO/} @list );

may give you this error:

    Array found where operator expected

which can be fixed by dropping the parentheses:

    ... Filter {y/aeiou/UAEIO/} @list;

So if you need or want to use parentheses when calling Filter, it is best
to also include the C<sub> keyword and the comma:

lib/Algorithm/Loops.pm  view on Meta::CPAN

if you write C<sub {> as part of building the list of items to be sorted
but you don't provide a comparison routine.  This bug means we can't
write the previous code as:

    my @sorted= Filter {
        s#\d{2}(\d+)#\1#g
    } sort Filter sub {
        s#(\d+)# sprintf "%02d%s", length($1), $1 #g
    }, @data;

because it will produce the following error:

    Undefined subroutine in sort

in some versions of Perl.  Some versions of Perl may even require you
to write it like this:

    my @sorted= Filter {
        s#\d{2}(\d+)#\1#g
    } sort &Filter( sub {
        s#(\d+)# sprintf "%02d%s", length($1), $1 #g

lib/Algorithm/Loops.pm  view on Meta::CPAN

    $iter= NestedLoops( \@Loops );
    $iter= NestedLoops( \@Loops, \%Opts );
    ...    NestedLoops( \@Loops, \%Opts, \&Code );
    ...    NestedLoops( \@Loops,         \&Code );

The "..."s above show that, when the final code reference is provided,
NestedLoops can return a few different types of information.

In a void context, NestedLoops simply iterates and calls the provided
code, discarding any values it returns.  (Calling NestedLoops in a void
context without passing a final code reference is a fatal error.)

In a list context, NestedLoops C<push>es the values returned by each call
to \&Code onto an array and then returns (copies of the values from) that
array.

In a scalar contetx, NestedLoops keeps a running total of the number of
values returned by each call to \&Code and then returns this total.  The
value is the same as if you had called NestedLoops in a list context and
counted the number of values returned (except for using less memory).