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Re^5: two order sort

by AnomalousMonk (Abbot)
on Mar 05, 2013 at 07:04 UTC ( #1021762=note: print w/ replies, xml ) Need Help??


in reply to Re^4: two order sort
in thread two order sort

# Decending numeric and descending alpha ... pack 'Na4a*', -(0+$_), ~substr( $_, 1), $_ ... ;; 0uvmu 0dvys 0cjlf 9klou 9ijei 8klfd ... 1imwi 1akkn

I think you fixed a  -substr( $_, 1) (- vice ~) that was there originally, but I was still puzzled by the sorting of 0 before 9 in an otherwise descending numeric sort. Looking at the bit fields in detail tells the tale: the  -(0+$_) expression should be  ~(0+$_) instead (in this particular case at least) to produce an effective descending numeric ordering from an actual ascending lexicographic sort.

>perl -wMstrict -le "print unpack 'H*', pack 'N', -0; print unpack 'H*', pack 'N', -1; print unpack 'H*', pack 'N', -2; print unpack 'H*', pack 'N', -9; print unpack 'H*', pack 'N', -10; print ''; ;; print unpack 'H*', pack 'N', ~0; print unpack 'H*', pack 'N', ~1; print unpack 'H*', pack 'N', ~2; print unpack 'H*', pack 'N', ~9; print unpack 'H*', pack 'N', ~10; " 00000000 ffffffff fffffffe fffffff7 fffffff6 ffffffff fffffffe fffffffd fffffff6 fffffff5
>perl -wMstrict -le "use List::Util qw(shuffle); ;; my @a = qw( 0uvmu 3rqhx 8klfd 2uwep 9klou 3jrkx 6excm 1imwi 7axqf 1lpys 0dvys 3ozcw 7lbhj 1pjzw 9ijei 3hiyn 3vkon 1akkn 0cjlf 3myrn ); ;; @a = shuffle @a; ;; print for map{ unpack 'x[Na4]a*', $_ } sort map{ local $^W; pack 'Na4a*', ~(0+$_), ~substr( $_, 1), $_ } @a " 9klou 9ijei 8klfd 7lbhj 7axqf 6excm 3vkon 3rqhx 3ozcw 3myrn 3jrkx 3hiyn 2uwep 1pjzw 1lpys 1imwi 1akkn 0uvmu 0dvys 0cjlf

Hmmm...     This is trickier than it looks. And it looks kinda tricky. (And I don't say that my little fix is general.)


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Re^6: two order sort
by BrowserUk (Pope) on Mar 05, 2013 at 15:11 UTC

    You're right of course. You need ~ for both. (Seems I also forgot the details :)


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