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I have a Perl hash whose keys start with, or are, numbers.
If I use,
foreach my $key (sort keys %hash) {
print $hash{$key} . "\n";
}
the list might come out as,
0
0001
1000
203
23
Instead of
0
0001
23
203
1000
636
Because a hash is unsorted, if it's contents are required in a particular order then they must be sorted on output. Perl uses the '%' symbol as the variable sigil for hashes.
First sort the keys by the associated value. Then get the values (e.g. by using a hash slice). my @keys = sort { $h{$a} <=> $h{$b} } keys(%h); my @vals = @h{@keys};
Perl's built in sort function allows us to specify a custom sort order. Within the curly braces Perl gives us 2 variables, $a and $b, which reference 2 items to compare. In our case, these are hash references so we can access the elements of the hash and sort by any key we want.
foreach my $key (sort { $a <=> $b} keys %hash) {
print $hash{$key} . "\n";
}
The sort operation takes an optional comparison "subroutine" (either as a block of code, as I've done here, or the name of a subroutine). I've supplied an in-line comparison that treats the keys as numbers using the built-in numeric comparison operator '<=>'.
200
Paul's answer is correct for numbers, but if you want to take it a step further and sort mixed words and numbers like a human would, neither cmp nor <=> will do. For example,
9x
14
foo
fooa
foolio
Foolio
foo12
foo12a
Foo12a
foo12z
foo13a
Sort::Naturally takes care of this problem, providing the nsort and ncmp routines.
23
answered Sep 28 '22 08:09
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