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

Hi Good Monks, I want to print the number of elements in an array. 

print @my_array; # no good: "print" works in a list context 

print ($#my_array + 1); # OK only if "$[" set to 0

print (0 + @my_array); # works, but looks ugly

[download]
There must be some better way to force @my_array as a scalar or do I have flashbacks of "C" ???

I must be missing something ... actually I'm missing a lot of things :-)

Life is tough, it's tougher when you are dumb...

jfl

Replies are listed 'Best First'.
Re: Printing the length of an array ?
by kyle (Abbot) on Mar 30, 2008 at 20:50 UTC

    print scalar @my_array; (see scalar).

[reply]
[d/l]
      Thanks kyle !

      Exactly what I wanted, short and sweet..

      Totally forgot about the "scalar" operator (if I ever knew about it)

      Life is tough, it's tougher when you are dumb...

      jfl

[reply]
Re: Printing the length of an array ?
by FunkyMonk (Bishop) on Mar 30, 2008 at 21:00 UTC
    There's ways other than kyle's very reasonable suggestion of scalar. You just have to force scalar context. Here's a couple of different ways that spring to mind: 
    print 0+@my_array;
print "length = " . @my_array;

    [download]

[reply]
[d/l]
[select]
Re: Printing the length of an array ?
by jwkrahn (Abbot) on Mar 30, 2008 at 22:20 UTC
    updated ... twice 
    $ perl -le'my @array = qw/1 2 3 4 5 6 7/; print ~~@array'
7

$ perl -le'my @array = qw/1 2 3 4 5 6 7/; print -(-@array)'
7

$ perl -le'my @array = qw/1 2 3 4 5 6 7/; print 0+@array'
7

$ perl -le'my @array = qw/1 2 3 4 5 6 7/; print 1*@array'
7

$ perl -le'my @array = qw/1 2 3 4 5 6 7/; print @array/1'
7

$ perl -le'my @array = qw/1 2 3 4 5 6 7/; print @array-0'
7

$ perl -le'my @array = qw/1 2 3 4 5 6 7/; print @array x1'
7

$ perl -le'my @array = qw/1 2 3 4 5 6 7/; print @array%~0'
7

$ perl -le'my @array = qw/1 2 3 4 5 6 7/; print @array**1'
7

    [download]
[reply]
[d/l]
      $ perl -le'my @array = qw/1 2 3 4 5 6 7/; print -+- @array'
7

      [download]
[reply]
[d/l]
Re: Printing the length of an array ?
by ww (Archbishop) on Mar 30, 2008 at 21:14 UTC
    or, perhaps canonically, but definitely NOT canonically (see FunkyMonk's below), 
    #! /usr/bin/perl
use strict;
use warnings;

my @array = qw/1 2 3 4 5 6 7/;

print "number of elements is " . ++$#array . "\n";

    [download]

    The increment is necessary because the first element is @array[0].

    This produces:

    ww@GIG:~/pl_test$ perl elementsinarray.pl
number of elements is 7

    [download]
[reply]
[d/l]
[select]
      The ++ makes the array one element longer, adding an undef at the end: 
      my @array = qw/1 2 3 4 5 6 7/;
print "number of elements is " . ++$#array . "\n";
print Dumper \@array;

      [download]

      number of elements is 7
$VAR1 = [
          '1',
          '2',
          '3',
          '4',
          '5',
          '6',
          '7',
          undef
        ];

      [download]

[reply]
[d/l]
[select]
        Correct!

        Better, and clearer, to write for line 7:

        my $count = $#array;
print "number of elements is " . ++$count . "\n";

        [download]
[reply]
[d/l]
Re: Printing the length of an array ?
by Jenda (Abbot) on Mar 31, 2008 at 17:51 UTC
[reply]
[d/l]
[select]

Back to Seekers of Perl Wisdom