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
views:
919answers:
2
+16
A:
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 '<=>'.
Paul Tomblin
2008-12-20 17:56:49
To clarify a bit: the keys in your case are strings, and are sorted as strings. <=> operator interprets its arguments as numbers, converting strings to numbers as needed.This is the sense of much of perl's oddness: operators, rather than variables, are typed in perl.
Arkadiy
2008-12-20 18:26:00
It's context rather than type. <=> evaluates it's operands in numeric context, while the default sort operator (cmp) evaluates them in scalar (i.e. string) context.
kixx
2008-12-20 21:15:40
+4
A:
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.
Schwern
2008-12-22 03:14:02