Question

I have some code that’s working, but spitting out a lot of warnings.

    foreach my $item ( sort {$item_rank{$a} <=> $item_rank{$b}} @items{
        ...
    }

My problem is that not every item has a rank, and so my output is littered with warnings. I want to make the items with no rank last.
I am thinking of changing the code to as follows:

    foreach my $item ( sort {
                              $item_rank{$a} = 99999 if(!exist $item_rank{$a});
                              $item_rank{$b} = 99999 if(!exist $item_rank{$b});
                              $item_rank{$a} <=> $item_rank{$b}} @items{
        ...
    }

My question is, is there a particular value that I can set it to instead of 99999, although I will never reach 99999 in my current setup, I want my code more robust.

Thanks

Answer 1

You can do it one of 2 ways:

• If you have defined max ceiling, default to it (To simplify the code, I am assuming 0 is not a valid rank)

  $max_ceiling = 99999;
  sort { ($item_rank{$a} || $max_ceiling)
     <=> ($item_rank{$b} || $max_ceiling) } @items
  

  Or, to avoid assigning to the hash:

  # Ideally, %item_rank should be passed as a parameter but meh.
  sub rank4comp { exist $item_rank{$_[0]} ? $item_rank{$_[0]} : 999999; }
  sort { rank4comp($a) <=> rank4comp($b) } @items;
  

• Better yet, check for undefs explicitly in your expression (remember that sort’s code block can be ANY expression, which returns negative, 0 or positive ala “<=>“:

  sort { defined $item_rank{$a}
       ? defined $item_rank{$b}
       ? $item_rank{$a} <=> $item_rank{$b} : 1 : -1 } @items;