Re: compare two sorted array, item by item, which one is bigger

In our last episode, the evil Dr. Lacto had captured our hero,
  Rainer Weikusat <[email protected]>, who said:
> hymie! <[email protected]> writes:
>> The question is -- how can I (or can I) programatically keep checking
>> entries in the arrays of the %scores hash until I find a pair of
>> entries that are not equal?
>
> If your arrays are always of equal length, you could use

I don't think I can depend on that :(

> otherwise, it's a bit more difficult.
>
> sub ary_cmp
> {
>     my ($a0, $a1) = @_;
>     my ($last, $rc);
>
>     # we need the length of the shorter array
>     # start with the length of array a0
>     # and see if the length of array a1 is less
>     $last = $#$a0;
>     $_ < $last and $last = $_ for $#$a1;
>
>     # for each entry in the shorter array
>     # compare that numbered entry in the two arrays
>     # return <=> if the result is not 0
>     for (0 .. $last) {
>         $_ and return $_ for $$a0[$_] <=> $$a1[$_];
>     }
>
>     # all of the elements are equal, so return the longer array
>     return @$a0 <=> @$a1;
> }

I took the liberty of adding your improvement to this function.

I'll definitely try this out and see how well it work.

I have a few followup questions...

(*) I added some comments.  Can you tell me if I'm correct?

(*) Could I have set $last this way?

$last = $#$a0 < $#$a1 ? $#$a0 : $#$a1 ;

or

$last = @$a0 < @$a1 ? @$a0 : @$a1 ;

?

(*) In this construct

>     for (0 .. $last) {
>         $_ and return $_ for $$a0[$_] <=> $$a1[$_];

is it safe to reuse $_ like that?  The scoping will work itself out,
even without a bracket set?

Thank you very much.

--hymie!