my ($class,@args)=@_;
    my $line;
    my $self = $class->SUPER::new(@args);
    my ($file)=$self->_rearrange(['FILE'], @args);
    $self->_initialize_io(@args) || warn "Did you intend to use STDIN?"; #Read only for now
    #Remove header
    do {
	$line=$self->_readline;
	chomp $line;
	push @{$self->{unstructured}},$line if (length($line)>2); } until ($line =~ m{^//}) || (!defined($line)); #Unstructured header
    $self->_initialize;
    return $self;

    my $self=shift;
    my $line;
    return if ($self->{end});
    my (@a,@c,@g,@t, $id, $tr1, @refs,$accn, $bf, $sites);
    my $i=0;
    while (defined( $line=$self->_readline)) {
	chomp($line);
	if ($line=~/^\d{2}/) {	#Begining of the frequency data
	    ($a[$i],$c[$i],$g[$i],$t[$i])=_parse_matrix($line);
	    $i++;
	}
	($tr1,$accn)=split(/\s{2}/,$line) if ($line=~/^AC\s/);
	($tr1,$bf)=split(/\s{2}/,$line) if ($line=~/^BF\s/);
	($tr1,$id)=split(/\s{2}/,$line) if ($line=~/^ID\s/);
	last if (($line=~/^XX/) && ($i>0));
    }
    if (!(defined($id) && defined($accn))) {
	$self->{end}=1;
	return;
    }
    while (defined( $line=$self->_readline)) {	#How many sites?
	if ($line=~/^BA\s/) {
	    my ($tr1,$ba)=split(/\s{2}/,$line);
	    ($sites)=split(/\s/,$ba);
	}
   if ($line=~/^RN/) { #Adding a reference as Bio::Annotation object (self)
    # not interested in RN line itself, since has only transfac-specific
    # reference id? - no push back of line
    my $ref=_parse_ref($self);
    push @refs,$ref
  }
	last if ($line=~m{^//});
    }
    # We have the frequencies, let's create a SiteMatrix object
    my %matrix = &_make_matrix($self,\@a,\@c,\@g,\@t,$id, $accn);
    $matrix{-sites}=$sites if ($sites);
    $matrix{-width}=@a;
    my $psm=new Bio::Matrix::PSM::Psm(%matrix);
    foreach my $ref (@refs) { $psm->add_Annotation('reference',$ref); }
    return $psm;

    my $line=shift;
    $line=~s/\s+/,/g;
    my ($tr,$a,$c,$g,$t)=split(/,/,$line);
    return $a,$c,$g,$t;

    my ($a, $c, $g, $t, @fa, @fc,@fg, @ft, @a,@c,@g,@t);
    my $ave=0;
    my ($self,$cA,$cC,$cG,$cT, $id, $accn)= @_;

    for (my $i=0; $i < @{$cA};$i++) {
	#No value can be undefined -throw an exception, since setting to 0 probably would be wrong
  #If this happens it would indicate most probably that the file, being parsed is in a different format
	map {  $self->throw('Parsing error, a position is not defined') unless  defined(${$_}[$i]) } ($cA, $cG, $cC, $cT);
	
	if ( (${$cA}[$i] + ${$cC}[$i] + 
	      ${$cG}[$i] + ${$cT}[$i] ) ==0 ) {
	    push @a,$ave;
	    push @c,$ave;
	    push @g,$ave;
	    push @t,$ave;
	}
	else {
	    push @a,${$cA}[$i];
	    push @c,${$cC}[$i];
	    push @g,${$cG}[$i];
	    push @t,${$cT}[$i];
	    $ave = ((${$cA}[$i]+${$cC}[$i]+
		     ${$cG}[$i]+${$cT}[$i]) / 4 +$ave)/2;
	}
    }

    for (my $i=0; $i<@a;$i++) {
	my $zero=($a[$i]+$c[$i]+$g[$i]+$t[$i]);
	next if ($zero==0);
	push @fa, $a[$i];
	push @fc, $c[$i];
	push @fg, $g[$i];
	push @ft, $t[$i];
    }
    return (-pA=>\@fa,-pC=>\@fc,-pG=>\@fg,-pT=>\@ft, -id=>$id, -accession_number=>$accn)

my $self=shift;
my ($authors,$title,$loc,@refs,$tr,$db,$dbid);
    while (my $refline=$self->_readline) { #Poorely designed, should go through an array with fields
      chomp $refline;
      my ($field,$arg)=split(/\s+/,$refline,2);
      last if ($field=~/XX/);
      $field.=' ';
      REF: {
          if ($field=~/RX/) {  #DB Reference
              $refline=~s/[;\.]//g;
              ($tr, $db, $dbid)=split(/\s+/,$refline);
              last REF;
          }
         if ($field=~/RT/) {   #Title
            $title .= $arg;
            last REF;
          }
          if ($field=~/RA/) {  #Author
            $authors .= $arg;
            last REF;
          }
          if ($field=~/RL/) {  #Journal
            $loc .= $arg;
            last REF;
          }
        }
     }
     my $reference=new Bio::Annotation::Reference (-authors=>$authors, -title=>$title,
                                                    -location=>$loc);
     if ($db eq 'MEDLINE') {
        # does it ever equal medline?
        $reference->medline($dbid);
     }
     elsif ($dbid) {
        $reference->pubmed($dbid);
     }
     return $reference;

    my $self=shift;
    $self->close;

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  http://bugzilla.open-bio.org/

 Title   : _parseMatrix
 Usage   :
 Function: Parses a line
 Throws  :
 Example :  Internal stuff
 Returns :  array (frequencies for A,C,G,T in this order).
 Args    :  string