package Matrix;
use strict;
use warnings;
use Exporter qw<import>;
our @EXPORT_OK = qw<row column>;

sub define_matrix {
    my @matrix;
    # shift is just the parameter that was passed to the subroutine
    # split on the newline
    my @lines = split /\n/, shift;
    # push into the matrix a reference to an array which represents
    # each row.  Elements of the array are found by splitting on
    # blank space
    push @matrix, [split / /] foreach (@lines);
    return @matrix;
}

# $input is a reference to a hash with two keys:
# index, which asks for a row or column, and
# string, which represents the matrix

sub row {
  my ($input) = @_;
  my $index  = $input->{'index'};
  my @matrix = define_matrix($input->{'string'});
  # since we are returning a row, $index-1 is the row within @matrix
  # we need to return.  In this case, we are returning a reference to
  # an array which contains the element of the row
  return $matrix[$index - 1];
}

sub column {
  my ($input) = @_;
  my $index  = $input->{'index'};
  my @matrix = define_matrix($input->{'string'});
  my @column;
  # each row of the matrix is represented by an array.  $row is a
  # reference to that array.  To get the column, we use [$index-1].
  foreach my $row (@matrix) {
      push @column, $row->[$index - 1];
  }
  # we need to return a reference to the array containing the column
  return \@column;
}

1;