Re^3: How to create a hash whose values are undef?

If you want to initialise the values to some other value, say zero, for example:

my %hash;
@hash{@keys} = (0) x @keys;
[download]

The LHS is a slice, on the RHS the value, 0, is in parentheses which generates a list, the @keys is used in scalar context to get the correct number of values.

Comment on Re^3: How to create a hash whose values are undef? Download Code

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Re^4: How to create a hash whose values are undef? by Marshall (Canon) on Jul 06, 2009 at 12:11 UTC
Great! I like your thinking, but you should be aware that "0" and even "" is not the same as "undef". `#!/usr/bin/perl -w use strict; use Data::Dumper; my @keys = (1,2,3); my %hash; @hash{@keys} = (undef) x @keys; print Dumper \%hash; __END__ Prints: $VAR1 = { '1' => undef, '3' => undef, '2' => undef };` [download]	[reply] [d/l]
Re^5: How to create a hash whose values are undef? by cdarke (Prior) on Jul 07, 2009 at 07:36 UTC
Exactly (that's why I said "some other value"). Otherwise it could be done thus: `my %hash; @hash{@keys} = undef;` [download] No need for the x operator. This sets the first value to undef, the others are unspecified so are set to undef as well.	[reply] [d/l]