how do i sort hash by key numerically

[Anonymous Monk]

if i have

%hash={ 89=>3,
    45=>2,
    1 =>5,
    40=>3}

i want the output as

1=>5,
40=>3,
45=>2,
89=>3}

how do i do it.

Originally posted as a Categorized Question.

[Jouke]

This would do the trick:


#!/usr/bin/perl -w
%hash=( 89=>3, 45=>2, 1 =>5, 40=>3);
foreach (sort { $a <=> $b } keys(%hash) )
{
    print "key: $_ value: $hash{$_}\n"
}

Jouke Visser, Perl 'Adept'

[Tyke]

Are you sure that this doesn't sort typographically rather than numerically. I think the {$a<=>$b} block cited by arhuman is necessary here.

-- 
I knock my pate and fancy wit will come
Knock as I please, there's no one at home
      a pontiff paraphrased

[arhuman]

for $key ( sort {$a<=>$b} keys %hash) {
           print "($key)->($hash{$key})\n";
}

[arhuman]

I've set {$a<=>$b} to show you how to change the way the list should be sorted...
You could sort on :
key decreasing order : {$b<=>$a}
values-> {$hash{$a}<=>$hash{$b}}
key length -> {length{$a}<=>length{$b}}
or whatever...

[tomhukins]

Effective Perl Programming's sorting recipes explains in details how you might approach this problem.

[planetscape]

That link is b0rked (at least ATM). Another that might help is: Perl Sorting Techniques.

HTH,

[Anonymous Monk]

Note that while second answer produces your test output, it does NOT sort the keys numerically. Show this by strengthening your test with another key=>val pair 100=>100 and see that 100 sorts before 40.

Originally posted as a Categorized Answer.

[bose]

hello everyone, your answer is ok,but i want to sort the above array by values.here '3' is two times then how?

[Corion]

See perlfaq4 on How do I sort a hash.