Best Of Perl 6 Tablet: Revision 11 / Perl 6

Perl 6

Best Of Perl 6 Tablet: Revision 11

Overview - Chapter: 0:Intr, 1:Hist, 2:Design, 3:Var, 4:Op, 5:IO, 6:{}, 7:Sub, 8:OOP, 9:Rx - Appendices: A:Index, B:Tables, C:Best of, D:Delta, E:Links

Command Line
File IO
Automatic multithreading
Comparison
Case construct
Powerful for loops
Named parameters in subroutines
Objects with auto generated new and getters and setters

This is a small tour, showing the best features and improvements of Perl 6 in short examples, compared to similar working Perl 5 examples.

Output

Making output will become simpler and easier for newbies.

Perl 5(.8)	Perl 6
print "bananas are good\n";	say "bananas are good";
print "and I said: ".$quotes{"me"}.".\n";	say "and I said: {%quotes<me>}.";

File IO

File::Slurp is in the Perl 6 core language and file reading is simpler then ever (and autochomp included).

Perl 5	Perl 6
open my $FH, '<', "poetry.txt";	$content = slurp "poetry.txt";
read $FH, $content, $block_len until eof;
close $FH;
open my $FH, '<', "poetry.txt";	@content = lines "poetry.txt";
while (<$FH>) { chomp; push @content, $_; }
close $FH;

Automatic multithreading

Applying operations to junctions and arrays is now syntactically compact and readable. Perl 6 will create threads where appropriate to use multiple processors, cores or hyperthreading for high level language SIMD concurrent processing.

Perl 5	Perl 6
my $sum;	my $sum = [+] @numbers;
$sum += $_ for @numbers;
for (0 .. $#factor1) {	@product = @factor1 >>*<< @factor2;
$product[$] = $factor1[$] * $factor2[$_];
}

The Perl 5 code is a simplification, of course Perl6 "does the right thing" when the arrays have different lengths.

Comparsion

Here are junctions, then chained comparison operators.

Perl 5	Perl 6
if ($a = 3 or $a = 4 or $a = 7) {...}	if $a = 3	4	7 {...}
{{if (4 < $a and $a < 12) {...}	if 4 < $a < 12 {...}
if (4 < $a and $a <= 12) {...}	if $a ~~ 4^..12 {...}

The err operator eases lot of cases where Perl 5 newbies could fall into traps.

Perl 5	Perl 6
$a = defined $b ? $b : $c;	$a = $b // $c;

Case construct

Perl 5	Perl 6
if ($a = 2 or $a = 5) {...}	given $a {
elseif ($a = 6 or $a = 7 or $a = 8 or $a = 9) {...}	when 2	5 {...}
elseif ($a =~ /g/) {...}	when 6 .. 9 {...}
else {...}	when 'g' {...}
	default {...}
	}

It's clear to read, very versatile and when used in combination with junctions, becomes even clearer.

powerful for loops

Perl 5	Perl 6
for my $i (1..15) {...}	for 1..15 -> $i {...}
for (my $i=15; $i>1; $i-2) {}	for 1..15:by(-2)- > $i {...}
for my $key (keys %hash) {	for %hash.kv -> $key, $value {
print "$key => $hash{$key}\n"; ...	say "$key => $value"; ...
for my $i (0..$#a) {	for zip(@a; @b; @c)- > $a, $b, $c {...}
my $a = @a[$i];
my $b = @b[$i];
my $c = @c[$i];
...

named parameters in subroutines

Perl 5:

sub routine {
my $a = shift;
my $b = shift;
my @rest = @_;
}

Perl 6:

sub routine ($a, $b, *@rest) {...}

Objects with auto generated new and getters and setters

Simple Object creation is now as easy as it gets.

Perl 5:

package Heart::Gold;

sub new {
bless {speed => 0 }, shift;
}

sub speed {
my $self = shift;
my $speed = shift;
if (defined $speed) { $self->{speed} = $speed }
else { $self->{speed} }
}

sub stop {
my $self = shift;
$self->{speed} = 0;
}