Re: Sorting a hash

On Jun 2, 8:43 pm, [email protected] (Jialin Li) wrote:
> On Mon, Jun 2, 2008 at 1:53 PM, Iain Adams <[email protected]> wrote:
> > Hello,
>
> > I am trying to sort a hash of hashes.
>
> > my code looks like this
>
> >  foreach $cnt (sort keys %{ $relations{ $uid }{ "instances" } }){
> >             print OUT "$cnt 1, ";
> >  }
>
> > This prints out the correct numbers (the keys of the instances hash.
> > However the sorting is a bit weird.  The keys are all integers yet
> > when sorting the keys aren't put in number order. instead the first
> > digit is seen as the qualifier.
>
> > Here is an example output:
>
> >  100 1, 120 1, 121 1, 122 1, 123 1, 124 1, 125 1, 126 1, 127 1, 132 1,
> > 133 1, 134 1, 135 1, 136 1, 137 1, 138 1, 139 1, 221 1, 222 1, 223 1,
> > 224 1, 225 1, 226 1, 227 1, 228 1, 235 1, 236 1, 237 1, 238 1, 239 1,
> > 240 1, 241 1, 242 1, 323 1, 324 1, 325 1, 326 1, 327 1, 328 1, 329 1,
> > 330 1, 50 1, 51 1, 52 1, 53 1, 54 1, 55 1, 56 1, 57 1, 93 1, 94 1, 95
> > 1, 96 1, 97 1, 98 1, 99 1,
>
> > As you can see it is not in normal order.
>
> > Does anyone know why this is happening and how I can fix it?
>
> > Thanks
>
> > --
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> >http://learn.perl.org/
>
> to numerically sort, you should use:
>
> sort { $a <=> $b } keys %{ $relations{ $uid }{ "instances" }  }
>
> when you omit { $a <=> $b }, perl is using default string comparison:
> { $a cmp $b}
>
> Jialin

Thanks Jialin thats great!