Problem with passing array in a sub

SHKVal has asked for the wisdom of the Perl Monks concerning the following question:

Hello. I tried to pass an array in my sub as a separate set of args, but discovered that the hole array is a first element of the @_. I cant pick the elements up from @_[ 0] because I use recursion and the sub waits for separate args. So I need to fix the problem only on the first call. Here is some code.

sub permutations {
  my @array = @_;
  #my @tmp = @_;
  #if ($tmp[0][1] != 0) { for (0..$#{$tmp[0]}) { push (@array, $tmp[0]
+[$_]); } }
  #else { @array = @_; }
  if ($#array == 0) {return [ $array[0] ]; }
  my @results;
  my $element;
  foreach $element (0..$#array) {
    my @leftovers = @array;
    my $chosen_one = splice(@leftovers, $element, 1);
    foreach (&permutations(@leftovers)) {
      push(@results, [ $chosen_one, @{$_} ]);
    }
  }
  return @results;
}

@a = permutations($test[2]);
[download]

where @test is a 2-dimentional array.

Comment on Problem with passing array in a sub Download Code

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Re: Problem with passing array in a sub by choroba (Cardinal) on May 30, 2014 at 08:15 UTC
If @test is a 2d array, then passing `$test[2]` to the subroutine passes an array reference, not an array. To pass the array, you have to dereference it: `@a = permutations(@{ $test[2] });` [download] See perllol - Manipulating Arrays of Arrays in Perl for details. لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l] [select]
Re: Problem with passing array in a sub by perlfan (Parson) on May 30, 2014 at 12:16 UTC
If `@test` contains arrays as elements, then these are actually arrayrefs. Therefore, you must dereference each element using `my @row3 = @{ $test[2] };` [download] This is how nested data structures work in Perl.	[reply] [d/l] [select]
Re: Problem with passing array in a sub by RonW (Parson) on May 30, 2014 at 16:47 UTC
As previously stated, you are passing a reference, not a list. It is also possible to conditionally dereference in your sub: `if (ref($_[0])) { @array = @{$_[0]}; }` [download]	[reply] [d/l]
Re: Problem with passing array in a sub by SHKVal (Initiate) on May 30, 2014 at 14:32 UTC
Thanks to everyone, this works.)	[reply]