%hash = map { $_ => 1 } @array;
is just a funny way to write
%hash = ();
foreach $_ (@array) {
$hash{$_} = 1;
}
-----Original Message-----
From: Sharan Basappa [mailto:[EMAIL PROTECTED]
Sent: 20 March 2008 15:47
To: Chas. Owens
Cc: Robert Leibl; Perl Beginners
Subject: Re: find an entry in hash array
Can you throw some light on this statement:
my %hashset = map { $_ => 1 } @array;
On Thu, Mar 20, 2008 at 9:14 PM, Chas. Owens <[EMAIL PROTECTED]>
wrote:
> On Thu, Mar 20, 2008 at 11:35 AM, Sharan Basappa
>
> <[EMAIL PROTECTED]> wrote:
>
> > Well here is what I am trying to do.
> > I have an array (generated from somewhere) I would like to convert
> > this into an associative array and then based on some other input
> > I would like to see if an entry exists in the asso array. As you
> can see > the value does not really matter. What matters is whether
> the entry > exists or not.
> > For example (very trivial one)
> > I have a list of names that are allowed access to a machine. I
> create a asso > array of them. Later when I want to check if the
> user is allowed to login, I > check if that user exists or not.
> Currently I am doing this by making value for > key as 1. But I
never really use the value at all.
> > Regards
> snip
>
> This data structure is called a hash set. Hash sets are easy to make
in Perl:
>
> #!/usr/bin/perl
>
> use warnings;
> use strict;
>
> my @array = qw<a d f h>;
> my %hashset = map { $_ => 1 } @array; for my $letter ("a" .. "i") {
> if (exists $hashset{$letter}) {
> print "$letter is in the hash set\n";
> } else {
> print "$letter is not in the hash set\n";
> }
> }
>
> a is in the hash set
> b is not in the hash set
> c is not in the hash set
> d is in the hash set
> e is not in the hash set
> f is in the hash set
> g is not in the hash set
> h is in the hash set
> i is not in the hash set
>
>
> --
>
>
> Chas. Owens
> wonkden.net
> The most important skill a programmer can have is the ability to
read.
>
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