Beefy Boxes and Bandwidth Generously Provided by pair Networks
Your skill will accomplish
what the force of many cannot
 
PerlMonks  

need an explanation

by Lennotoecom (Pilgrim)
on Sep 22, 2013 at 21:50 UTC ( #1055202=perlquestion: print w/replies, xml ) Need Help??
Lennotoecom has asked for the wisdom of the Perl Monks concerning the following question:

Hi, can you explain please
how exactly this snippet works,
and if possible context transformation:
@a = qw(a b c d e); $b = () = @a; # $b now is 5
Thanks!

update:
$b = @a;
would do the same effect,
so basically there is no need for ();
but still, the question remains if someone got
any explanation

update update:
thank you for answer Mr. Choroba
yes indeed that was just the wrong example that was used by some fellow
your last example was helpful
thank a lot

Replies are listed 'Best First'.
Re: need an explanation
by choroba (Chancellor) on Sep 22, 2013 at 21:55 UTC
    The first line is equivalent to
    @a = ('a', 'b', 'c', 'd', 'e');

    qw just "quotes words".

    The second line is usually written as

    $b = @a;

    or, for more clarity,

    $b = scalar @a;

    Perl is sensitive to context. By assigning to a scalar value, you impose the scalar context on the right hand side of the assignment. Arrays return their size (number of elements) in scalar context. Using = () = here has no effect and is only confusing. Update: It is usually used to force list context, for example

    $x = () = "abcdABCabA" =~ /a/ig; # Count A's regardless of case.
    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: perlquestion [id://1055202]
Approved by Albannach
help
Chatterbox?
and all is quiet...

How do I use this? | Other CB clients
Other Users?
Others avoiding work at the Monastery: (2)
As of 2017-08-23 22:40 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    Who is your favorite scientist and why?



























    Results (360 votes). Check out past polls.

    Notices?