Re^6: Sorting based on any column

Its giving error "Use of uninitialized value in numeric comparison (<=>)"

That's because this is almost certainly not doing whatever you think it's doing:

$ab = "\$a";
[download]

That's taking the value of $a and appending it to a backslash and making it the value of $ab, so "11" becomes "\11". I'm guessing that you're trying to make $ab a reference to $a, but to do that you'd need to leave out the quotes, and that would also change the later code.

Personally, if I wanted to have a toggle between two different ways to sort, I'd do it like this (unless the sort comparison is very complex, in which case it should be in a separate subroutine anyway):

sub sort_array_by_column_asc_or_desc {
  my( $array, $column, $order ) = @_;
  if( $order eq 'desc' ){
    return sort { put_descending_sort_comparison_here } @$array;
  } else {    # default to ascending sort
    return sort { put_ascending_sort_comparison_here } @$array;
  }
}
[download]

Note: the else there isn't necessary, but I like it because it makes the choice obvious.

Aaron B.
Available for small or large Perl jobs and *nix system administration; see my home node.

Comment on Re^6: Sorting based on any column Select or Download Code

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Re^7: Sorting based on any column by AnomalousMonk (Archbishop) on May 21, 2015 at 15:08 UTC
`$ab = "\$a";` That's taking the value of $a and appending it to a backslash ... Actually, it's escaping a `$` (dollar) character to make it a literal rather than a scalar sigil, which would result in scalar interpolation: `c:\@Work\Perl\monks>perl -wMstrict -le "my $a = 'foo'; my $ab = qq{'\$a' '$a'}; print $ab; " '$a' 'foo'` [download] (I have to use `qq{}` instead of `""` (double-quotes) to keep Windoze command line from going nuts with escapes.) Give a man a fish: `<%-(-(-(-<`	[reply] [d/l] [select]
Re^8: Sorting based on any column by aaron_baugher (Curate) on May 21, 2015 at 21:46 UTC
Oh, of course. That's what I get for not trying it once to make sure. Thanks for correcting both my mistakes in this thread. Aaron B. Available for small or large Perl jobs and *nix system administration; see my home node.	[reply]


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