JupiterHost.Net wrote:
>> On Oct 3, JupiterHost.Net said:
>>
>>> I have a list of strings that start with an uppercase B, Q, or Z
>>>
>>> I need to sort them so they are in order of Q, B , then Z
>>>
>>> Any ideas or input on how to efficiently do that with sort() or even
>>> map() is most appreciated :) perldoc -f sort|-f map didn't appear to
>>> address this situation :(
>
> Jeff 'japhy' Pinyan wrote:
>
>> I would use map() before and after sort() to "correct" leading
>> characters.
>>
>> my @sorted =
>> map { tr/123/QBZ/; $_ }
>> sort
>> map { tr/QBZ/123/; $_ }
>> @data;
>
> Xavier Noria wrote:
>
> > They all go in ASCII relative order except B <-> Q, thus a way to
> get > it is to handle that special case and delegate to cmp the rest:
> >
> > my @sorted = sort {
> > my $x = substr($a, 0, 1) . substr($b, 0, 1);
> > $x eq "BQ" || $x eq "QB" ? $b cmp $a : $a cmp $b;
> > } @array;
> >
> > I used the concatenation for clarity, you see the idea anyway if
> that's > too expensive for your usage.
>
> Brilliant! I'll benchmark those ideas :) Thanks you two!
Read this for an explanation of Jeff's solution:
http://en.wikipedia.org/wiki/Schwartzian_transform
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