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Non-deprecated way to capture array length
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| Marc Sacks 2006-10-12, 6:59 pm |
| I needed to find out the length of an array and did it by referencing
the array in scalar context. However, "use warnings" indicated that this
is a deprecated feature. Is there a non-deprecated way to do this
(other than looping through the whole array until I run out of
elements)? Thanks.
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| Jeff Pang 2006-10-12, 6:59 pm |
|
>I needed to find out the length of an array and did it by referencing
>the array in scalar context. However, "use warnings" indicated that this
>is a deprecated feature. Is there a non-deprecated way to do this
>(other than looping through the whole array until I run out of
>elements)? Thanks.
>
How do you write it? I can get it like:
$ perl -Mstrict -Mwarnings -le 'my @arr=qw/aa bb cc/;print length(join "",@arr)'
6
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Jeff Pang
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| Derek B. Smith 2006-10-12, 6:59 pm |
| --- Marc Sacks <msacks@lextranet.com> wrote:
> I needed to find out the length of an array and did
> it by referencing
> the array in scalar context. However, "use warnings"
> indicated that this
> is a deprecated feature. Is there a non-deprecated
> way to do this
> (other than looping through the whole array until I
> run out of
> elements)? Thanks.
>
Hi Mark,
the best practice/standard way to get an array length
is:
print scalar @array_name,"\n";
or
my $array_lnght = scalar @array_name;
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| |
| John W. Krahn 2006-10-12, 6:59 pm |
| Marc Sacks wrote:
> I needed to find out the length of an array and did it by referencing
> the array in scalar context. However, "use warnings" indicated that this
> is a deprecated feature. Is there a non-deprecated way to do this
> (other than looping through the whole array until I run out of
> elements)? Thanks.
Using an array in scalar context is *not* deprecated.
Since you haven't shown any code I would have to guess that you are using
defined() on an array which *is* deprecated.
John
--
Perl isn't a toolbox, but a small machine shop where you can special-order
certain sorts of tools at low cost and in short order. -- Larry Wall
| |
| Jeff Pang 2006-10-12, 6:59 pm |
|
>
>
>How do you write it? I can get it like:
>
>$ perl -Mstrict -Mwarnings -le 'my @arr=qw/aa bb cc/;print length(join "",@arr)'
>6
>
Sorry, if you mean the number of elements in an array,then it should be:
my $num = scalar @array;
--
Jeff Pang
NetEase AntiSpam Team
http://corp.netease.com
| |
| Kim Helliwell 2006-10-12, 6:59 pm |
|
-----Original Message-----
From: Jeff Pang [mailto:pangj@earthlink.net]=20
Sent: Monday, October 09, 2006 7:48 AM
To: beginners
Subject: Re: Non-deprecated way to capture array length
>
this=20[color=darkred]
>
>How do you write it? I can get it like:
>
>$ perl -Mstrict -Mwarnings -le 'my @arr=3Dqw/aa bb cc/;print =
length(join
"",@arr)' =20
>6
>
Sorry, if you mean the number of elements in an array,then it should be:
my $num =3D scalar @array;
--
Jeff Pang
NetEase AntiSpam Team
http://corp.netease.com
--=20
Perhaps I'm behind the times here, but what's wrong with:
my $num =3D $#array
??
That's how I always do it.
Kim Helliwell
LSI Logic Corporation
Work: 408 433 8475
Cell: 408 832 5365
kim.helliwell@lsi.com
=20
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| |
| Jeff Pang 2006-10-12, 6:59 pm |
|
>--
>Perhaps I'm behind the times here, but what's wrong with:
>
>my $num = $#array
>
>??
[coremail@admin ~]$ perl -Mstrict -Mwarnings -le 'my @arr=qw/aa bb cc/;print $#arr'
2
[coremail@admin ~]$ perl -Mstrict -Mwarnings -le 'my @arr=qw/aa bb cc/;print scalar @arr'
3
They are not the same.
The $#arr is the last element's index number,while 'scalar @arr' is all the elements' total number.
--
Jeff Pang
NetEase AntiSpam Team
http://corp.netease.com
| |
| Kim Helliwell 2006-10-12, 6:59 pm |
| -----Original Message-----
From: Jeff Pang [mailto:pangj@earthlink.net]=20
Sent: Monday, October 09, 2006 8:25 AM
To: beginners
Subject: RE: Non-deprecated way to capture array length
>--=20
>Perhaps I'm behind the times here, but what's wrong with:
>
>my $num =3D $#array
>
>??
[coremail@admin ~]$ perl -Mstrict -Mwarnings -le 'my @arr=3Dqw/aa bb
cc/;print $#arr' =20
2
[coremail@admin ~]$ perl -Mstrict -Mwarnings -le 'my @arr=3Dqw/aa bb
cc/;print scalar @arr'
3
They are not the same.
The $#arr is the last element's index number,while 'scalar @arr' is all
the elements' total number.
--
Jeff Pang
NetEase AntiSpam Team
http://corp.netease.com
--=20
Oops, you're right! Guess I'm still half asleep this morning.
But $#arr + 1 is surely another way to get the result sought.
That's the way I always do it, not realizing that scalar @arr
was even available, I guess. However, scalar @arr is computationally
more efficient, I bet, and only slightly longer to write. So it's
probably a better way.
I'm not exactly a Perl beginner, but looks like I learned something
already from this list. Pretty good, seeing I only signed up 3 days
ago....
Kim Helliwell
LSI Logic Corporation
Work: 408 433 8475
Cell: 408 832 5365
kim.helliwell@lsi.com
To unsubscribe, e-mail: beginners-unsubscribe@perl.org
For additional commands, e-mail: beginners-help@perl.org
<http://learn.perl.org/> <http://learn.perl.org/first-response>
| |
| John W. Krahn 2006-10-12, 6:59 pm |
| Marc Sacks wrote:
> John W. Krahn wrote:
>
>
> Actually, what I did was something like
"what I did was something like" is not the same as "this is the actual code
that produced the warning".
> my @arr = (a,b,c,d,e);
> $length = $arr;
@arr and $arr are two separate variables, the second of which is not even an
array. There is nothing in that example that should produce a warning message.
John
--
Perl isn't a toolbox, but a small machine shop where you can special-order
certain sorts of tools at low cost and in short order. -- Larry Wall
| |
| Uri Guttman 2006-10-12, 6:59 pm |
| >>>>> "KH" == Kim Helliwell <Kim.Helliwell@lsil.com> writes:
KH> Oops, you're right! Guess I'm still half asleep this morning.
KH> But $#arr + 1 is surely another way to get the result sought.
KH> That's the way I always do it, not realizing that scalar @arr
KH> was even available, I guess. However, scalar @arr is computationally
KH> more efficient, I bet, and only slightly longer to write. So it's
KH> probably a better way.
you rarely need the scalar() call to get an array length. most times you
will be using it in a scalar context like:
$len = @array ;
for my $i ( 1 .. @array ) { ...
using scalar when it isn't needed just adds noise. so learn more about
perl contexts which will help you.
uri
--
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--Perl Consulting, Stem Development, Systems Architecture, Design and Coding-
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| |
| Paul Lalli 2006-10-12, 6:59 pm |
| John W. Krahn wrote:
>
> @arr and $arr are two separate variables, the second of which is not even an
> array. There is nothing in that example that should produce a warning message.
where "nothing" == 7, I assume?
$ perl -we'
my @arr = (a, b, c, d, e);
$length = $arr;
'
Unquoted string "a" may clash with future reserved word at -e line 2.
Unquoted string "b" may clash with future reserved word at -e line 2.
Unquoted string "c" may clash with future reserved word at -e line 2.
Unquoted string "d" may clash with future reserved word at -e line 2.
Unquoted string "e" may clash with future reserved word at -e line 2.
Name "main::length" used only once: possible typo at -e line 3.
Name "main::arr" used only once: possible typo at -e line 3.
Paul Lalli
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