Beefy Boxes and Bandwidth Generously Provided by pair Networks
Problems? Is your data what you think it is?
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

To expound on demerphq's response with an example:

Given a hash, like so:

my %test; $test{a} = 1; $test{b} = 2;
When you call a subroutine with an array or hash, it gets flattened into a list. For a hash, that means giving all of its keys and corresponding values. So this:
something(%test);
is the same as this:
something(a, 1, b, 2);
(Note that when hashes are flattened, the keys may come out in any order, so it could have also been something(b, 2, a, 1);.)

The other side of this situation is that you can fill a hash directly with a list, instead of doing each key one-at-a-time. When you assign to a hash with a list, each odd item becomes a key, and the corresponding even item is its value. So we could have filled the hash like this:

%test = (a, 1, b, 2);
and it would be exactly the same. Note that this is also the same as the more familiar:
%test = (a => 1, b => 2);
as the => is just a type of comma that auto-quotes its left side operand. Now you can see what happens:
something(%test); # is like something(a, 1, b, 2);
And inside the sub:
my %hash = @_; # is like %hash = (a, 1, b, 2);
And so it turns out that you're just doing a basic copy. The hash inside the sub will be a copy of the one you passed in.


In reply to Re: Re: Perl Internals: Hashes by kelan
in thread Perl Internals: Hashes by Kozz

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others wandering the Monastery: (7)
    As of 2014-10-23 02:48 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      For retirement, I am banking on:










      Results (123 votes), past polls