sub binsearch(&\@) {
   my ($compare, $array) = @_;

   my $i = 0;
   my $j = $#$array;
   return $j if $j == -1;

   for (;;) {
      my $k = int(($i+$j)/2);

      my $cmp;
      $cmp = $compare->() for $array->[$k];
      return $k if !$cmp;

      if ($cmp < 0) {
         $j = $k-1;
         return _unsigned_to_signed(~$k) if $i > $j;
      } else {
         $i = $k+1;
         return _unsigned_to_signed(~$i) if $i > $j;
      }
   }
}

sub _unsigned_to_signed { unpack('j', pack('J', $_[0])) }