What does $#variable mean?

Scarborough has asked for the wisdom of the Perl Monks concerning the following question:

I've worked with Perl for a couple of years but have just found this

$LENDERCOUNT = $#SORTEDLENDERS;
[download]

In some code I am checking. I belive that SORTEDLENDERS is an array. I can't ask the orginal programmer so I am hoping that a monk maybe able to help. $LENDERCOUNT ends up as 1 or -1 when I have run this with -d

update (broquaint): added <code> tags

Thank you all for your Help

20040320 Edit by jeffa: Changed title from 'Whats happening here'

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Re: What does $#variable mean? by Limbic~Region (Chancellor) on Mar 19, 2004 at 16:10 UTC
Scarborough, That is Perl making your life easy. The intent is to prevent the programmer from having to keep track of indices. `my @array = qw(one two three); my $last_index = $#array; # Index of last element (2) my $last_element = $array[ -1 ]; # Value of last element (three)` [download] And then of course there is push, pop, shift, unshift to make your life easier as well. Cheers - L~R Update: Some other helpful things to remember `my $count = @array; # Number of elements (3) $#array = 99; # Extend/Truncate array` [download]	[reply] [d/l] [select]
Re: What does $#variable mean? by Rich36 (Chaplain) on Mar 19, 2004 at 16:11 UTC
$#SORTEDLENDERS indicates that there's an array @SORTEDLENDERS. The $#arrayname syntax holds the index of the last member of an array. `my @array = ('foo', 'bar', 'baz'); # $#array = 2 # because Perl's array indexes start at 0` [download] «Rich36»	[reply] [d/l]
Re: What does $#variable mean? by pbeckingham (Parson) on Mar 19, 2004 at 16:11 UTC
The construct you see is returning the index of the last element in the array, which is one less than the number of elements in the array. `my @array = (1, 2, 3); print $#array, "\n";` [download] will print "2".	[reply] [d/l]
Re: What does $#variable mean? by dws (Chancellor) on Mar 19, 2004 at 16:55 UTC
In case it's slipped by in the answers above, `$LENDERCOUNT` does not get the count of elements in `@SORTEDLENDERS`. It gets the last index, which will be one less than the number of elements. You may be looking at an off-by-one bug. The correct way of getting the count of elements in an array is: `$LENDERCOUNT = @SORTEDLENDERS;` [download]	[reply] [d/l] [select]
Re: What does $#variable mean? by tinita (Parson) on Mar 19, 2004 at 16:13 UTC
it's the last index of the array @SORTEDLENDERS. so if it has 5 elements, the last index would be 4, as indizes are from 0..4. in case the array is empty the last index is -1. for details (and exceptions) please refer to perldata	[reply]
Re: What does $#variable mean? by pelagic (Priest) on Mar 19, 2004 at 16:14 UTC
quote from "Learning Perl": `You can use $#fred to get the index value of the last element of @fred +.` [download] pelagic ------------------------------------- I can resist anything but temptation.	[reply] [d/l]
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