doubts in references

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

Dear Monks

Now i started learning the references in perl and it looks handy in some critical situations in coding.

I have some doubts in references.

print @{[%hash]}

The above coding prints the hash.

But i didn't able to get the concept in this reference.

Please explain me how it works.

Thanks in advance

Prasad

_{janitored by ybiC: Retitle from "reference" because one-word nodetitles hinder site searching}

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Re: doubts in reference by ccn (Vicar) on Sep 27, 2004 at 11:39 UTC
%hash in list context is evaluated as a list of (key , value) pairs a list in brackets `[list]` -- is a reference to anonymous array @{} -- is dereference of reference to an array	[reply] [d/l]
Re: doubts in reference by Happy-the-monk (Canon) on Sep 27, 2004 at 11:45 UTC
ccn told you what it does. But actually what it does is `print %hash;` # prints hash as a list of its keys and values. - as in - `print @{ [ %hash ] }` # prints hash as a list of its keys and values. `[ ... ]` # an array reference is created... and `@{ ... }` # that array reference is de-referenced... it is no more. Cheers, Sören	[reply]
Re^2: doubts in reference by Grygonos (Chaplain) on Sep 27, 2004 at 18:55 UTC
That's a neat trick you can use for obfu code. do something and then undo it before the statement terminates. Theoretically you could add `[]` and `@{}` indefinitely to the outter bounds of the hash and it would still be fine.. Grygonos	[reply] [d/l] [select]
Re: doubts in reference by zejames (Hermit) on Sep 27, 2004 at 11:40 UTC
update : taken into account davorg's remarks. Internally, a hash table can be thought of a sort a "special" list. That means the following hash `%hash = ('test' => '24', 'blah' => '253');` [download] can be equivalent to `@hash = ('test', '24', 'blah', '253');` [download] BTW, `=>` is equivalent to `,` here. So if you understand that a hash is a special representation for an list, then you expression does the following : Take the array reference corresponding to the hash : `%hash` Derefence it and print it out. That is, you convert an hash to a array using the references. HTH -- zejames	[reply] [d/l] [select]
Re^2: doubts in reference by davorg (Chancellor) on Sep 27, 2004 at 11:50 UTC
I'm not really sure where slices come into it. I think you may have meant "list" instead of "slice". A hash can be created from a list of key/value pairs. And a hash evaluated in list context returns that same list (tho' perhaps in a different order). Slices don't enter into in at all. Please be a little more careful with your terminology. -- <http://www.dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply]