Perl 6, arrays, hashes, subroutines & basic file IO

Here is a small collection of Perl 6 code snippets lifted and mangled from pugs/examples/cookbook


# ARRAYS

my @a = <94 13 97 95>;

for @a -> $e {
    say $e;
}

# HASHES

my %hash = (
    'one'   => 'un',
    'two'   => 'deux',
    'three' => 'trois'
);

for %hash.keys -> $key {
    say "$key => %hash{$key}";
}

for %hash.kv -> $key, $value {
    say "The word '$key' is '$value' in French.";
}

# SUBROUTINES

sub perl5 {
    my ($x) = @_;
    say $x;
}

perl5('old-fashioned');

sub parameters ($foo) { say $foo }
parameters('some parameter');
parameters 'some parameter';
parameters foo => 'some parameter';
parameters :foo('some parameter');

sub whole (@names, %flags) {
    for @names -> $name { 
        say $name;
    }

    for (%flags.kv) -> $key, $value {
        say "$key => $value";
    }
}

my @stuff = ('array', 'elements');
my %flags = (hash => 'elements', are => 'pairs');

whole(@stuff, %flags);

sub optional ($required, $optional?) {
    my $second_arg = $optional // 'Told you it was optional!';
    say $required;
    say $second_arg;
}

optional('this');
optional('this', 'that');

sub named_params ($first, :$second, :$third) {
    say $first, $second, $third;
}

named_params(1, second => 2, third => 3);

sub transport ($planet, *@names) {
    say "Transporting to $planet:";
    for @names -> $name {
        say "\t$name";
    }
}

transport('Magrathea', 'Arthur', 'Ford', 'Ovid');

sub typed (Int $val) {
    say $val + 3;
}

typed(3);

# LOOP OVER STDIN

while $_ = =<> {
    .print;
}

# OPEN A FILE FOR READING

my $input = open("myfile.txt", :r) err die $!;

my $line = $input.readline;

$input.close;

# OPEN A FILE FOR WRITING

my $output = open("out.txt", :w) err die $!;

$output.say("blah");

$output.close;
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Comment on Perl 6, arrays, hashes, subroutines & basic file IO Download Code

Replies are listed 'Best First'.
Re: Perl 6, arrays, hashes, subroutines & basic file IO by lidden (Curate) on Nov 01, 2006 at 15:19 UTC
`print;` to print `$_` is now spelled `.print;` notice the dot.	[reply] [d/l] [select]
Re^2: Perl 6, arrays, hashes, subroutines & basic file IO by blazar (Canon) on Nov 01, 2006 at 15:51 UTC
print; to print $_ is now spelled .print; notice the dot. And also, with reference to the point you're actually referring to, `for` is now good for looping over a handle too, thanks to lazy evaluation, thus: `# LOOP OVER STDIN for =<> { .print; }` [download]	[reply] [d/l] [select]
Re: Perl 6, arrays, hashes, subroutines & basic file IO by zentara (Archbishop) on Nov 01, 2006 at 12:52 UTC
2 beginner questions on Perl6. 1. Where is the 'my' in those variable usages? 2. Why did they switch from 'print' to 'say'? It's shorter? I'm not really a human, but I play one on earth. Cogito ergo sum a bum	[reply]
Re^2: Perl 6, arrays, hashes, subroutines & basic file IO by BrowserUk (Patriarch) on Nov 01, 2006 at 13:24 UTC
The only 'variables' I see without `my` in those snippets are formal parameter names, which are declarative only? `say $var;` is equivalent to `print $var . $/;` Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal? "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re^2: Perl 6, arrays, hashes, subroutines & basic file IO by blazar (Canon) on Nov 01, 2006 at 15:43 UTC
Where is the 'my' in those variable usages? As BrowserUk wrote, I don't see any missing. While we're here I'll take a chance to remind that differently from Perl 5, Perl 6 has `strict` and `warnings` turned on by default except in particular situations, e.g. in oneliners, where it's most often better otherwise. Why did they switch from 'print' to 'say'? It's shorter? Err, well, yes: easy things should be easy. And Perl has been somehow missing a writeln/println statement for quite a long time. But as also pointed out by BrowserUk, they did not "switch": you will have both `print` and `say`. The interesting thing to note here is that iirc in conjunction with the use of the latter auto`chomp` actions are often taken, although it's not entirely clear to me how and when (I know the answer is out there I'm just too lazy ATM) - but it seems that $_ is not chomped by default: `pugs> say .chars for <foo bar baz>; 3 3 3 undef pugs> say .chars for =<>; foo 4 bar 4 baz 4` [download]	[reply] [d/l] [select]

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