in reply to Question: Is undef a valid argument?

Well, if you are just looking to check if there is anything in it or not (i.e. not checking to see the actual *number* of elements) according to defined :

"You should instead use a simple test for size: 
    if (@an_array) { print "has array elements\n" }

[download]
"
I suppose you could also do something like scalar(@an_array) to find out the number of elements it currently possesses.

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Re^2: Question: Is undef a valid argument?
by jujiro_eb (Sexton) on May 06, 2009 at 21:41 UTC
    Thanks JPerl!

    This is elegent and requires same lines of code as I used before.

    Ash

[reply]
Re^2: Question: Is undef a valid argument?
by jujiro_eb (Sexton) on May 06, 2009 at 21:54 UTC
    Sorry,

    Spoke too soon.

    None of what you sggested works.

    #! /usr/bin/perl
use strict;
use warnings;

sub p1 {
    my $n1;
    $n1=scalar(@_);
    if  (@_) {
        print "Has elements\n";    
    }
    
    print "1. Parameters to the sub p1 $n1\n";
    my $p1=shift;
    if  (@_) {
        print "Has elements\n";    
    }
    else {
        print "Has no elements\n";    
    }
    print "2. p1=$p1\n";
}
p1 $ARGV[0];

    [download]
    Try passing nothing to the script you will see it still states one argument.
[reply]
[d/l]

      Like I already said, $ARGV[0] always evaluates to a scalar. As long as you keep using $ARGV[0], you'll always get a scalar. If you want to pass zero when @ARGV is empty, you'll need to pass something different when @ARGV is empty. In general, you'd do 

      p1( @ARGV ? $ARGV[0] : () );

      [download]

      In this case, the following suffices: 

      p1(@ARGV);

      [download]
[reply]
[d/l]
[select]
      You are still explicitly passing the first, non existent element of your array to your subroutine. If instead call your subroutine with

      p1 @ARGV;

      you will get your expected result.

[reply]
[d/l]

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