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This means that the substr function will be called four times for each comparison, which could add up if it's a large array. That makes it a good candidate for a Schwartzian Transform. (You probably know that; I'm adding it for the original poster.) UPDATE: I was completely wrong about this; see below.

#!/usr/bin/env perl use Modern::Perl; use Data::Dumper; my @data = <DATA>; @data = map { $_->[0] } sort { $b->[1][0] <=> $a->[1][0] or $a->[1][1] <=> $b->[1][1] } map { [ $_, [substr( $_, 0, 8 ), substr( $_, 8)]] } @data; say @data; __DATA__ 20090405022300 20080405022600 20090405022900 20080405023500 20050405005000 20080405022500 20090405022500 20020405081200 20010405000000 20090405022100

UPDATE: While I understand the Schwartzian Transform in theory and think it's one of the coolest things ever, I haven't had much call to actually use it, so I did a benchmark for this case against the simple sort of substr calls. I was a little surprised to see that the repeated substr calls beat my ST, testing with array sizes from 10 to 1_000_000. In fact, the ST took about twice as long in all tests. I guess four substr calls (or two if the first comparison returns a value so the second comparison isn't necessary) don't qualify as expensive enough to make the overhead of the ST worth it here. Darn it.

Aaron B.
Available for small or large Perl jobs; see my home node.


In reply to Re^2: Date to be sorted in descending and time in ascending by aaron_baugher
in thread Date to be sorted in descending and time in ascending by karthik7887

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