last index of array ref...

cLive ;-) has asked for the wisdom of the Perl Monks concerning the following question:

Something seems counterintuitive about using $# with array refs:

my @array = (1,2,3,4,5,6,7);
print "scalar co
print "array last index - $#array\n";

my $arrayref = [1,2,3,4,5,6];

print "arrayref last index - $#$arrayref\n";
[download]

Why does this work? The syntax looks wrong to me?

cLive ;-)

update - looking at the array in scalar context makes it easier to see, but it still feels weird to me:

print "array scalar context - ".@array."\n";
print "arrayref scalar context - ".@$arrayref."\n";
[download]

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Re: last index of array ref... by borisz (Canon) on Apr 02, 2005 at 00:02 UTC
Maybe you find it easier with braces. `$aref = [qw/1 2 3/]; print $#$aref; print $#{$aref}; # it is not the same as scalar(@$aref) print scalar(@$aref);` [download] Boris	[reply] [d/l]
Re: last index of array ref... (4 rules) by tye (Sage) on Apr 02, 2005 at 03:37 UTC
References quick reference breaks dereferencing down into the 4 simple rules, which makes it easier to remember and less confusing. You case is covered by the first two rules. - tye	[reply]
Re: last index of array ref... by Roy Johnson (Monsignor) on Apr 01, 2005 at 23:55 UTC
$# works pretty much the same way @ does. You can stick either of them on a scalar variable hashref or on an array name. Caution: Contents may have been coded under pressure.	[reply]
Re: last index of array ref... by ikegami (Patriarch) on Apr 02, 2005 at 00:29 UTC
`@array vs @{$arrayref} $array[0] vs ${$arrayref}[0] $#array vs $#{$arrayref}` [download] It's definitely consistent. I don't see the problem.	[reply] [d/l]
Re: last index of array ref... by brian_d_foy (Abbot) on Apr 02, 2005 at 02:31 UTC
If the reference is in a simple scalar (so not a single element access to a hash, function return value, or something else), you can replace the name portion of the variable with the reference. Sometimes it looks weird, but I tell people to take a deep breath, then start from the inside. Isolate the reference, then find the other parts that gives away the variable type (like @, $#, or `[]` for arrays, % or {} for hashes, and so on). With practice, it gets better. :) -- brian d foy <brian@stonehenge.com>	[reply] [d/l]
Re: last index of array ref... by ysth (Canon) on Apr 02, 2005 at 01:17 UTC
That's the cardinal rule of references; wherever you'd have an array name (sans sigil), you can have $simple_scalar_holding_arrayref or {expression yielding arrayref}.	[reply]
Re: last index of array ref... by Anonymous Monk on Apr 02, 2005 at 06:47 UTC
Something seems counterintuitive -- Why? It works the same as with arrays.	[reply]