In Perl, how do I create a hash whose keys come from a given array?

Question

Let\'s say I have an array, and I know I\'m going to be doing a lot of \"Does the array contain X?\" checks. The efficient way to do this is to turn that array into a hash, wher

Answer 1

Raldi's solution can be tightened up to this (the '=>' from the original is not necessary):

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

This technique can also be used for turning text lists into hashes:

my %hash = map { $_,1 } split(",",$line)

Additionally if you have a line of values like this: "foo=1,bar=2,baz=3" you can do this:

my %hash = map { split("=",$_) } split(",",$line);

[EDIT to include]

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Another solution offered (which takes two lines) is:

my %hash;
#The values in %hash can only be accessed by doing exists($hash{$key})
#The assignment only works with '= undef;' and will not work properly with '= 1;'
#if you do '= 1;' only the hash key of $array[0] will be set to 1;
@hash{@array} = undef;