sub BinSearch
{
my ($target, $cmp) = @_;
my @array = @{$_[2]};

my $posmin = 0;
my $posmax = $#array;

return -0.5 if &$cmp (0, \@array, $target) > 0;
return $#array + 0.5 if &$cmp ($#array, \@array, $target) < 0;

while (1)
  {
  my $mid = int (($posmin + $posmax) / 2);
  my $result = &$cmp ($mid, \@array, $target);
  
  if ($result < 0)
    {
    $posmin = $posmax, next if $mid == $posmin && $posmax != $posmin;
    return $mid + 0.5 if $mid == $posmin;
    $posmin = $mid;
    }
  elsif ($result > 0)
    {
    $posmax = $posmin, next if $mid == $posmax && $posmax != $posmin;
    return $mid - 0.5 if $mid == $posmax;
    $posmax = $mid;
    }
  else
    {
    return $mid;
    }
  }
}