1 line array to hash converter

[rossta]

I have an array of numbers, and an empty hash:

my @array = (1..10);
my %hash = ();

I remember a one liner, that would populate the keys of the hash with the elements of the array, but now it escapes me (age?). I seem to remember it was something like:

%hash{@array} = (1) x scalar(@array};

But that doesn't work. Any ideas?

[stefp]

$hash{$_}++ for @array;

The value associated to a key is the number of elements in @array which have the value of the said key.

The solution you searched for and explicited by suaveant gives 1 for each value even if the key appears many times in the array.

TMTOWTDI.

-- stefp

[rossta]

Thanks everyone. I think stefp offered the most elegant solution, because: 1. Shortest amount of code. 2. Elegant and easy to read and understand. 3. Assigns something useful to the hash value. Of course, in hindsight, it was *obvious*.

[davorg]

If you only need to populate the keys of the hash, then

@hash{@array} = ();

will work. The values will all be undef.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you don't talk about Perl club."

[suaveant]

Almost!

@hash{@array} = (1) x scalar(@array};

need to put an @ at the front... not sure why, but you do

                - Ant
                - Some of my best work - Fish Dinner

[jeffa]

The @ sign pretty much tells the interpreter to expect a SLICE, and since hash is (hopefully) already defined as a hash, you get a hash slice. :)

japhy has a great little 'tutorial' i found (via google) at http://www.crusoe.net/~jeffp/docs/using_refs

jeffa

[davorg]

Actually, it's the type of brackets - {} - that tells Perl that's it's a hash slice.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you don't talk about Perl club."

[clintp]

Nit: useless use of scalar

@hash{@array}=(1) x @array;

Works peachy as well.

[thpfft]

How about the less glamorous:

my %hash = map { $_ => 1 } @array;

which gets you off the separate declaration of %hash and is more versatile in the long run. Or to make your example a real oneliner:

my %hash = map { $_ => 1 } (1..10);

But i assume that in something real you'd be using an array that existed already.