Natural sorting
In Perl6 it is very easy to modify the default sorting order by passing in a transform routine to the sort function. If the transform routines are arity one, the sort function will apply a Schwartzian Transform so it only needs to calculate the transform once. Note that the transforms are non-destructive; The sort function returns the original strings.
The following are a series of subroutines to perform the various natural sorting transforms. They may be applied individually or mixed and matched to get the particular result desired. When more than one is strung together, they apply left to right. Some combinations may yield different results depending on the order they are applied.
# Sort groups of digits in number order. Sort by order of magnitude then lexically.
sub naturally ($a) { $a.lc.subst(/(\d+)/, ->$/ {0~$0.chars.chr~$0},:g) ~"\x0"~$a }
# Collapse multiple ws characters to a single.
sub collapse ($a) { $a.subst( / ( \s ) $0+ /, -> $/ { $0 }, :g ) }
# Convert all ws characters to a space.
sub normalize ($a) { $a.subst( / ( \s ) /, ' ', :g ) }
# Ignore common leading articles for title sorts
sub title ($a) { $a.subst( / :i ^ ( a | an | the ) >> \s* /, '' ) }
# Decompose ISO-Latin1 glyphs to their base character.
sub latin1_decompose ($a) {
$a.trans: <
Æ AE æ ae Þ TH þ th Ð TH ð th ß ss À A Á A Â A Ã A Ä A Å A à a á a
â a ã a ä a å a Ç C ç c È E É E Ê E Ë E è e é e ê e ë e Ì I Í I Î
I Ï I ì i í i î i ï i Ò O Ó O Ô O Õ O Ö O Ø O ò o ó o ô o õ o ö o
ø o Ñ N ñ n Ù U Ú U Û U Ü U ù u ú u û u ü u Ý Y ÿ y ý y
>.hash;
}
# Used as:
my @tests = (
[
"Task 1a\nSort while ignoring leading spaces.",
[
'ignore leading spaces: 1', ' ignore leading spaces: 4',
' ignore leading spaces: 3', ' ignore leading spaces: 2'
],
{.trim} # builtin method.
],
[
"Task 1b\nSort while ignoring multiple adjacent spaces.",
[
'ignore m.a.s spaces: 3', 'ignore m.a.s spaces: 1',
'ignore m.a.s spaces: 4', 'ignore m.a.s spaces: 2'
],
{.&collapse}
],
[
"Task 2\nSort with all white space normalized to regular spaces.",
[
"Normalized\tspaces: 4", "Normalized\xa0spaces: 1",
"Normalized\x20spaces: 2", "Normalized\nspaces: 3"
],
{.&normalize}
],
[
"Task 3\nSort case independently.",
[
'caSE INDEPENDENT: 3', 'casE INDEPENDENT: 2',
'cASE INDEPENDENT: 4', 'case INDEPENDENT: 1'
],
{.lc} # builtin method
],
[
"Task 4\nSort groups of digits in natural number order.",
[
<Foo100bar99baz0.txt foo100bar10baz0.txt foo1000bar99baz10.txt
foo1000bar99baz9.txt 201st 32nd 3rd 144th 17th 2 95>
],
{.&naturally}
],
[
"Task 5 ( mixed with 1, 2, 3 & 4 )\n"
~ "Sort titles, normalize white space, collapse multiple spaces to\n"
~ "single, trim leading white space, ignore common leading articles\n"
~ 'and sort digit groups in natural order.',
[
'The Wind in the Willows 8', ' The 39 Steps 3',
'The 7th Seal 1', 'Wanda 6',
'A Fish Called Wanda 5', ' The Wind and the Lion 7',
'Any Which Way But Loose 4', '12 Monkeys 2'
],
{.&normalize.&collapse.trim.&title.&naturally}
],
[
"Task 6, 7, 8\nMap letters in Latin1 that have accents or decompose to two\n"
~ 'characters to their base characters for sorting.',
[
<apple Ball bald car Card above Æon æon aether
niño nina e-mail Évian evoke außen autumn>
],
{.&latin1_decompose.&naturally}
]
);
for @tests -> $case {
my $code_ref = $case.pop;
my @array = $case.pop.list;
say $case.pop, "\n";
say "Standard Sort:\n";
.say for @array.sort;
say "\nNatural Sort:\n";
.say for @array.sort: {.$code_ref};
say "\n" ~ '*' x 40 ~ "\n";
}
Sample output:
Output:
Task 1a
Sort while ignoring leading spaces.
Standard Sort:
ignore leading spaces: 4
ignore leading spaces: 3
ignore leading spaces: 2
ignore leading spaces: 1
Natural Sort:
ignore leading spaces: 1
ignore leading spaces: 2
ignore leading spaces: 3
ignore leading spaces: 4
****************************************
Task 1b
Sort while ignoring multiple adjacent spaces.
Standard Sort:
ignore m.a.s spaces: 4
ignore m.a.s spaces: 3
ignore m.a.s spaces: 2
ignore m.a.s spaces: 1
Natural Sort:
ignore m.a.s spaces: 1
ignore m.a.s spaces: 2
ignore m.a.s spaces: 3
ignore m.a.s spaces: 4
****************************************
Task 2
Sort with all white space normalized to regular spaces.
Standard Sort:
Normalized spaces: 4
Normalized
spaces: 3
Normalized spaces: 2
Normalized spaces: 1
Natural Sort:
Normalized spaces: 1
Normalized spaces: 2
Normalized
spaces: 3
Normalized spaces: 4
****************************************
Task 3
Sort case independently.
Standard Sort:
cASE INDEPENDENT: 4
caSE INDEPENDENT: 3
casE INDEPENDENT: 2
case INDEPENDENT: 1
Natural Sort:
case INDEPENDENT: 1
casE INDEPENDENT: 2
caSE INDEPENDENT: 3
cASE INDEPENDENT: 4
****************************************
Task 4
Sort groups of digits in natural number order.
Standard Sort:
144th
17th
2
201st
32nd
3rd
95
Foo100bar99baz0.txt
foo1000bar99baz10.txt
foo1000bar99baz9.txt
foo100bar10baz0.txt
Natural Sort:
2
3rd
17th
32nd
95
144th
201st
foo100bar10baz0.txt
Foo100bar99baz0.txt
foo1000bar99baz9.txt
foo1000bar99baz10.txt
****************************************
Task 5 ( mixed with 1, 2, 3 & 4 )
Sort titles, normalize white space, collapse multiple spaces to
single, trim leading white space, ignore common leading articles
and sort digit groups in natural order.
Standard Sort:
The 39 Steps 3
The Wind and the Lion 7
12 Monkeys 2
A Fish Called Wanda 5
Any Which Way But Loose 4
The 7th Seal 1
The Wind in the Willows 8
Wanda 6
Natural Sort:
The 7th Seal 1
12 Monkeys 2
The 39 Steps 3
Any Which Way But Loose 4
A Fish Called Wanda 5
Wanda 6
The Wind and the Lion 7
The Wind in the Willows 8
****************************************
Task 6, 7, 8
Map letters in Latin1 that have accents or decompose to two
characters to their base characters for sorting.
Standard Sort:
Ball
Card
above
aether
apple
autumn
außen
bald
car
e-mail
evoke
nina
niño
Æon
Évian
æon
Natural Sort:
above
Æon
æon
aether
apple
außen
autumn
bald
Ball
car
Card
e-mail
Évian
evoke
nina
niño
****************************************