On Aug 21, 2012, at 1:23 PM, Jim Gibson wrote:
>
> On Aug 21, 2012, at 1:05 PM, Chris Stinemetz wrote:
>
>> Hello List,
>>
>> I am trying to sort a hash of arrays ( example below: )
>>
>> I would the sort to sort in ascending order the first index of the array
>> then the second index of the array.
>
> I believe you mean "first element" rather than "first index". The first index
> of your array is 0, and sorting by the indices is a no-operation.
>
> What you want to do is sort the list of keys returned by the keys() function.
> You do this by supplying a subroutine reference to the sort function that
> returns a negative value, zero, or a positive value if the first key yields a
> value less than, equal to, or greater than the value produced by the second
> key. The user-supplied sort function is provided the two keys as the
> variables $a and $b.
>
> If you want to sort by the first element of the arrays referenced by the hash
> values, then you want the values $a->[0] and $b->[0].
Oops. That is incorrect. I forgot to include access to the hash:
$hash{$a}->[0] <=> $hash{$b}->[0]
Please modify the other references to hash data.
> Since in your case, these values are numbers rather than strings, you want to
> use the tri-level <=> operator (rather than the cmp operator used for
> strings.)
>
> Thus the expression
>
> sort { $a->[0] <=> $b-{0] } keys %hash;
>
> should return the keys in your desired order.
>
> If you want to include a secondary key, you evaluate an expression that
> compares another array element if the first array elements are equal. This
> expression will do that;
>
> $a->[0] <=> $b->[0] ||
> $a->[1] <=> $b->[1]
>
> I will leave it to you to write an actual program incorporating these ideas.
>
> If you want to test your two-key sort, you will need to include some test
> data in which two or more records have the same first element.
>
>>
>> So in this example the arrays would sort to:
>>
>> 97,2,120,65
>> 219,1,30,33
>> 280,3,230,90
>> 462,2,270,65
>>
>> $VAR1 = {
>> '462-2' => [
>> '462',
>> '2',
>> '270',
>> '65'
>> ],
>> '219-1' => [
>> '219',
>> '1',
>> '30',
>> '33'
>> ],
>> '280-3' => [
>> '280',
>> '3',
>> '230',
>> '90'
>> ],
>> '97-2' => [
>> '97',
>> '2',
>> '120',
>> '65'
>>
>> };
>>
>
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