in reply to 2D array ALL combinations

Algorithm::Loops's NestedLoops would handle this nicely. 

use Algorithm::Loops qw( NestedLoops );

my @AoA1 = (
   [ 'a', 'b', 'c' ],
   [ 'd', 'e', ''  ],
   [ 'f', 'g', ''  ],
   [ 'h', '',  ''  ],
);

my @AoA2 = NestedLoops(\@AoA1, sub { [ @_ ] } );

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To use less memory: 

use Algorithm::Loops qw( NestedLoops );

my @AoA1 = (
   [ 'a', 'b', 'c' ],
   [ 'd', 'e', ''  ],
   [ 'f', 'g', ''  ],
   [ 'h', '',  ''  ],
);

my @AoA2;
my $iter = NestedLoops(\@AoA1);
my @list;
while (@list = $iter->()) {
   push @AoA2, [ @list ];
}

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By the way, since you have two identical values in @{$AoA1[3]}, @AoA2 will contain many duplicates.

Untested.

Update: The above don't produce the results in the order you described. If the order matters, change

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Re^2: 2D array ALL combinations
by Anonymous Monk on Jun 13, 2007 at 18:01 UTC
    ikegami,

    The elements '' (AoA1[1][2], AoA1[2][2], AoA1[3][1] and AoA1[3][2]) refer to empty elements. I would like combinations to exclude the empty ones to be more productive (my AoA1 is big).

    Thanks for hints, best.

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      You could make a copy of AoA1 with them grepped out. 

      my @cleaned_AoA1 = map { grep length, @$_ } @AoA1;

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      If you don't mind being destructive, you could remove the blank elements from @AoA1. 

      foreach (@AoA1) {
   @$_ = grep length, @$_;
}

      [download]

      I'm afraid that's the best NestedLoops can do because it can't loop using iterators.

      Grepping them out on the fly won't save you any memory. 

      sub make_scrubber {
   my ($aref) = @_;
   return sub { [ grep length, @$aref ] };
}

my $iter = NestedLoops(
   [ map { make_scrubber($_) } @AoA1 ]
);

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