ATatweiden·May 31, 2022
Have you used Raku before? The new and improved regex syntax [1] IMHO completely obsoletes legacy PCRE. Writing regexes in other languages feels like stepping into an ICE vehicle after driving a Tesla: so crufty and old and obvious legacy.
Raku’s built-in grammars make parsers trivial to write. I effortlessly created two [2] — one for reordering fstab entries, and the other for converting human-readable LUKS offsets into cryptsetup sectors — on a lazy afternoon. Grammars in Raku make this second nature.
Then you have Raku’s multi-dispatch. It is more capable than Erlang/Elixir pattern matching:
# a list with at least one element, extracting the head and tail
multi sub tail(*@list ($head, *@tail)) { @tail }
multi sub tail(*@list) { @list }
[3]
==> tail()
==> say(); # []
[3, 4]
==> tail()
==> say(); # [
Read the rest
4]
# pattern matching with arbitrary guards
multi sub user($name where { is-valid-user($_) }) { $name.say }
multi sub user($name) { "invalid name: $name".say }
sub is-valid-user($name)
{
# notice the additive character class in this regex: “letters plus digits”
# fail the match if $name is root
try with $name ~~ /(<+:Letter +digit>+)/ { $0 ne 'root' or fail }; $!.not
}
user('name'); # name
user('1234'); # 1234
user('root'); # invalid name: root
class Coordinates
{
has $.latitude is required;
has $.longitude is required;
}
class City
{
has Str:D $.name is required;
has Str:D $.state is required;
has Str:D $.country is required;
has Coordinates:D $.coordinates is required;
}
my $latitude = -37.840935;
my $longitude = 144.946457;
my Coordinates $coordinates .= new(:$latitude, :$longitude);
my Str:D $name = 'Melbourne';
my Str:D $state = 'Victoria';
my Str:D $country = 'Australia';
my City $melbourne .= new(:$name, :$state, :$country, :$coordinates);
my City:D $sydney = do {
my Coordinates:D $coordinates = do {
my $latitude = -33.86514;
my $longitude = 151.209900;
Coordinates.new(:$latitude, :$longitude);
};
my Str:D $name = 'Sydney';
my Str:D $state = 'New South Wales';
my Str:D $country = 'Australia';
City.new(:$name, :$state, :$country, :$coordinates);
};
# deeply nested argument deconstruction
multi sub melbourne-or-bust(
City:D $city (
Str:D :$name where 'Melbourne',
Str:D :$state,
Str:D :$country,
:$coordinates (
:$latitude,
:$longitude
)
)
)
{
my $gist = qq:to/EOF/.trim;
Welcome to the city of $name. It’s located in $state, $country.
GPS coordinates: $latitude, $longitude
EOF
$gist.say;
}
multi sub melbourne-or-bust(City:D $city)
{
'This isn’t Melbourne.'.say;
}
melbourne-or-bust($melbourne); # Welcome to the city of Melbourne ...
melbourne-or-bust($sydney); # This isn’t Melbourne
> Perl 6 was treated as the successor of Perl 5 -- and that was the mistake. It meant Perl 5 started dying,
Perl 6 took a long time to make, but how much did that matter? What was Perl going to do about Rails, Clojure, Go, Rust, JS/TS, and more? The world of programming languages used to be a lot smaller than it is today.
> Perl 6 had a new different syntax.
Inline::Perl5 [3] allows running legacy Perl 5 code in Perl 6 codebases.
[1]: https://docs.raku.org/language/5to6-nutshell#Regular_express...
[2]: https://github.com/atweiden/voidvault
[3]: https://github.com/niner/Inline-Perl5