How can I assign the elements in an array to only the key values in a hash?

blackjudas has asked for the wisdom of the Perl Monks concerning the following question: ⭐ (hashes)

Replies are listed 'Best First'.
Re: How can I assign the elements in an array to only the key values in a hash?⭐ by ariels (Curate) on Apr 10, 2001 at 11:26 UTC
Least confusing and most idiomatic is `@hash{@keys} = ();` [download] Unlike arturo's code, it writes a list where it means to write a list. See MeowChow's comments; here all values get set to undef "implicitly".	[reply] [d/l]
Re: How can I assign the elements in an array to only the key values in a hash?⭐ by MeowChow (Vicar) on Mar 31, 2001 at 06:19 UTC
I prefer: `undef @hash{@array};` [download] While this does exactly the same thing as the above, the syntax of `@hash{@array} = undef` is misleading, since only the first hash value is explictly set to undef, while the rest are implicitly undef'd. Novices who see this code might later write the following, expecting it to set all hash values to 1: `@hash{@array} = 1;` [download] Of course, only the first hash value is set to 1 in this case, and the rest become undef. MeowChow s aamecha.s a..a\u$&owag.print	[reply] [d/l] [select]
(ar0n) Re: Answer: How can I assign the elements in an array to only the key values in a hash? by ar0n (Priest) on Mar 31, 2001 at 21:09 UTC
`@hash{@array} = (1) x @array;` [download] [ar0n]	[reply] [d/l]
Re: How can I assign the elements in an array to only the key values in a hash?⭐ by arturo (Vicar) on Mar 30, 2001 at 22:12 UTC
Use a hash slice : `my %hash; @hash{@array} = undef;` [download]	[reply] [d/l]
Re: How can I assign the elements in an array to only the key values in a hash? by stefp (Vicar) on Mar 31, 2001 at 20:59 UTC
Q: I have an array that keeps returning matches in a string, each match must be inserted into a hash as an empty key (..) If i judge by your code, you want empty values. Anyway empty keys does not make sense. Because each key of a hash must be unique within the hash set of keys `$hash{$_}= '' for @array;` usually conunting number of matches for each strings makes more sense: `$hash{$_}++ for @array;` -- stef	[reply] [d/l] [select]
Re: Answer: How can I assign the elements in an array to only the key values in a hash? by Benedictine Monk (Novice) on Apr 01, 2001 at 08:47 UTC
If you're just trying to remove duplicates from the array (which I'm not sure you are), you can do this: my @array = getMatches(); my %tmp; @tmp{@array} = (undef) x @array; @array = keys %tmp; undef %tmp; This takes advantage of Perl's hash slices and can be incredibly useful for set-like operations. Jerry Goure	[reply]
Re: How can I assign the elements in an array to only the key values in a hash? by Madam (Sexton) on Mar 09, 2006 at 08:48 UTC
It may be too late to answer,but still.., `my %hash1 = map {$_ =>1 } @array;` [download]	[reply] [d/l]


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