Re: use Sort::Key

What should happen in this case?

my @data;
foreach ( 1 .. 100 ) {
    push @data, [ map { rand(200) - 100 } 1 .. 100 ];
}

my $pivot = 0;
my @sorted = keysort {
    my $v = $_;
    my @v = keysort { $_ > $pivot ? 1 : -1 } @{$v};
    $v[50]
} @data;
[download]

My wife's blog

Comment on Re: use Sort::Key Download Code

Replies are listed 'Best First'.
Re^2: use Sort::Key by salva (Canon) on Apr 16, 2005 at 10:40 UTC
well, what are you trying to do? The inner keysort on your code is equivalent to: `@v=((grep { $_ <= $pivot } @$v), (grep { $_ > $pivot } @$v));` [download] is that what you intended? I suppose that what you really want is to mimic the sort on the original post but numerically: sort first the elements > $pivot and then the rest. Then, for your specific data, integers between -100 and 100, this works: `my @v=nkeysort { $_<$pivot ? $_ + 200 : $_ } @$v;` [download] but if you know nothing about the numbers in $@v, then figuring a convenient sorting key can be quite difficult, it's easier to just use a grep/sort combination: `my @v=((sort {$a<=>$b} (grep { $_ >= $pivot } @$v)), (sort {$a<=>$b} (grep { $_ < $pivot } @$v)));` [download] that inserted on the outer sort becomes: `my @sorted = nkeysort { ( ( sort {$a<=>$b} (grep { $_ >= $pivot } @$_) ), ( sort {$a<=>$b} (grep { $_ < $pivot } @$_) ) )[50] } @data;` [download] BTW, note that for numeric keys you have to use nkeysort.	[reply] [d/l] [select]
Re^3: use Sort::Key by dragonchild (Archbishop) on Apr 18, 2005 at 12:38 UTC
I'm trying to see if you know what should happen if you have a keysort within a keysort. You built your module based on the &@ prototype. You don't have a test for a keysort in a keysort, to make sure you don't trip anything, especially on earlier implementations of prototypes (like 5.6.0). You should have a test for that. :-) My wife's blog	[reply]