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Re^2: Dictionary-style sort a la Tcl?

by Rohaq (Initiate)
 on Feb 02, 2012 at 15:09 UTC ( #951460=note: print w/replies, xml ) Need Help??

in reply to Re: Dictionary-style sort a la Tcl?
in thread Dictionary-style sort a la Tcl?

Wow, I feel like the ultimate necroposter here.

I stumbled across this solution, and found it fell over when it met the likes of the following:

```qw{
1.01
1.3
1.02
1.2
}
\$A <=> \$B does a numerical comparison, but strips any leading zeroes from the number, so how 1.02 and 1.2 are sorted will depend on their original order in the list - Tcl's dictionary sort doesn't seem to do this, and will place 1.2 above 1.02 in the sort.

So I extended your example to check for the string length of the compared numbers if they match numerically - If they match numerically, but have differing string lengths, then one must have leading zeroes. I also implemented the code into a subroutine:

```sub dict_sort {
my @unsorted = @_;
my @sorted =
map \$_->[0],
sort {
my \$i = 0;
{
my \$A = \$a->[1][\$i];
my \$B = \$b->[1][\$i];
defined(\$A) || defined(\$B)       # Stop if both undef
and (
defined(\$A) <=> defined(\$B)  # Defined wins over undef
or (
\$A !~ /\d/ || \$B !~ /\d/ # \$A or \$B is non-integer
?    (lc \$A cmp lc \$B)   # ?? Stringy lowercase
|| (   \$A cmp    \$B)   #    -> Tie breaker
: \$A <=> \$B              # :: \$A and \$B are integers
or (
length(\$A) <=> length(\$B)  # If numeric comparison ret
+urns the same, check length to sort by leading zeroes
)
)
or ++\$i && redo              # tie => next part
);
}
}
map [ \$_, [ split /(\d+)/ ] ], @unsorted;
return @sorted;
}

I'm not sure that this thread will ever get any more posts, but hopefully this helps somebody out!

Replies are listed 'Best First'.
Re^3: Dictionary-style sort a la Tcl?
by Anonymous Monk on Feb 04, 2012 at 09:39 UTC

I stumbled across this solution, and found it fell over when it met the likes of the following: qw{ 1.01 1.3 1.02 1.2 };

\$A <=> \$B does a numerical comparison, but strips any leading zeroes from the number, so how 1.02 and 1.2 are sorted will depend on their original order in the list

No, the spaceship operator  <=> does no stripping of any kind, it does a numerical comparison, and numbers don't have leading zeros , 0002 is 02 is 2

The problem is with the code/regex, which turns decimals into an array of integers , and then does a numerical comparison on each portion -- not gonna work

I'm not too familiar with Tcl's sort order, but what works for me (esp for mp3s) is to lowercase the string, and pad all digits with zeroes (sometimes 6, sometimes 20)

```#!/usr/bin/perl --
use strict; use warnings;
my @list = ( qw{
bigBoy bigbang bigboy x10y x9y x11y
1.01   1.3   1.02   1.2
x1.1y x1.01y x2.3y x2.1y } );

print join "\n",
map { \$\$_[0] }
sort { \$\$a[1] cmp \$\$b[1] }
map {
my \$f = \$_;
\$f =~ s/(\d+)/sprintf '%06d',\$1/ge;
[ \$_, lc \$f ]
} @list;
__END__
1.01
1.02
1.2
1.3
bigbang
bigBoy
bigboy
x1.1y
x1.01y
x2.1y
x2.3y
x9y
x10y
x11y
Sorry, I guess I could have worded that better - it doesn't 'strip' leading zeroes, it just ignores them as it's doing a numerical comparison. In any case, the change I added seems to make the sort identical to the Tcl dictionary sort. I'm not sure about yours.

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