# Clue interpreter
# written by Keymaker

local(*FH);
open(FH, $ARGV[0]) or do { print "Error in reading the program.\n"; exit 1; };
my $clue = do { local($/); <FH> };
close(FH);

$c = -1;
if($ARGV[1] ne ""){
  if($ARGV[1] =~ /^[0-9]*$/){
    $c = $ARGV[1];
  }
}

sub getnext{
  $v = $_[0] + 1;
  if($v >= length($clue)){
    $v=0;
  }
  $v;
}

if($clue =~ /^([01]*)$/){
  $clue = $1;
  $m = 0;
  $n = 0;
  while(length($clue) > 0){
    if($c > 0){
      $c--;
    }elsif($c == 0){
      print "Interpreter terminated due to the given limit.\n";
      exit 0;
    }

    print "$clue\n";
    if(substr($clue, $n, 1) eq "1"){
      $a = getnext($n);
      $b = getnext($a);
      $x = substr($clue, $a, 1);
      $y = substr($clue, $b, 1);

      if($x eq "1" && $y eq "1"){
        $v = "0";
      }else{
        $v = "1";
      }

      $clue = $v . $clue;
      $n = getnext($b + 1);
    }else{
      $clue = substr($clue, 0, length($clue)-1);
      $n = getnext($n);
    }
    $m++;
  }
  print "Program halted on cycle $m.\n";
}else{
  print "Error, program not valid.\n"; exit 1;
}