Dereferencing Perl hashrefs

Question

Using Text::Ngram I have

my $c = ngram_counts($text, 3);
my %ct = %($c);

which doesn't work (Scalar found where operator expected). I think this is a combination of not knowing what I'm doing (still not very good with Perl) and being confused about what exactly I'm getting as output from Text::Ngram. Help? I just want to look at the generated n-grams:

my @keys = sort {$ct{$a} cmp $ct{$b} } keys %ct;
foreach my $k (@keys) {
    print "$k: $ct{$k}\n"
}

Edit: Stupid error on my part, thanks everyone.

score 16 · Accepted Answer · answered Jul 22 '11 at 18:24

16

Use curly braces to dereference the hash reference:

my %ct = %{ $ct };  # %$ct would also work

And you probably want to use <=> for numerical sorting instead of the ASCII-betical sorting cmp.

answered Jul 22 '11 at 18:24

Zaid

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score 7 · Answer 2 · answered Jul 22 '11 at 18:23

7

Use curly braces:

my %ct = %{ $c };

answered Jul 22 '11 at 18:23

gpojd

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score 3 · Answer 3 · answered Jul 22 '11 at 18:41

There's no need to make a copy into another hash, just use the reference.

my $c = ngram_counts($text, 3);

my @keys = sort {$c->{$a} <=> $c->{$b} } keys %$c;
foreach my $k (@keys) {
    print "$k: $c->{$k}\n"
}

See http://perlmonks.org/?node=References+quick+reference for some easy to remember rules for dealing with references.

score 0 · Answer 4 · answered Jul 22 '11 at 18:25

0

Would you try this?

my $c = ngram_counts({}, $text, 3);

answered Jul 22 '11 at 18:25

sergio

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Dereferencing Perl hashrefs

4 Answers4