But when decalared this way it gives a warning message :"Use of
uninitialized value in concatenation (.) or string at"
in a print statement which is something like this :
my %myhash = map { $_ => undef } qw/A B C D E F G H I J
K/;
foreach my $key (%myhash){
print $myhash{$key}
}
-----Original Message-----
From: Paul Lalli [mailto:[EMAIL PROTECTED]
Sent: Friday, June 01, 2007 4:39 PM
To: beginners@perl.org; [EMAIL PROTECTED]
Subject: Re: Simplest hash initialization with no value
On Jun 1, 6:08 am, [EMAIL PROTECTED] (Alok Nath) wrote:
> Why it gives syntax error when -
> my @myhash{qw/A B/} = ();
Er... because it's not valid syntax. That's why you'd get a syntax
error. Not sure what you're asking. You can't "declare" a hash slice.
You declare variables.
> It works when I say -
> my %myhash ;
> @myhash{qw/A B/} = ();
Right. Because that is valid syntax. First you declare %myhash, then
you initialize two keys of that hash using a slice.
Your original question was "how to initialize a hash". It's apparent
now that you wanted to know how to "declare and initialize a hash in one
step". This question comes up so frequently that it really should be a
FAQ. The way you did so was fine originally. What's wrong with it? If
you have a longer list of keys, you could use the map operator as a
shortcut, so you don't write 'undef' multiple times:
my %myhash = map { $_ => undef } qw/A B C D E F G H I J K/;
Paul Lalli
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