Good Evils in PerlKang-min Liu <gugod@gugod.org>

$speaker.meta• 劉康民

Kang-min Liugugod

• http://gugod.org

• http://twitter.com/gugod

• gugod@gugod.org

• http://handlino.com/和多股份有限公司

perl is...

get things done

glue languagee

TIMTOWTDIThere is more then one way to do it

the good perl

pragma

Module::Acmepragma

pragma = one small english word.

Module = title-cased

just an convention.

warningsgives you good warning messages

#!/usr/bin/perlprint $foo;print "Hello";

Can anyone tell me if there’s any problem in this small program ?

foo.pl

strict

#!/usr/bin/perluse warnings;

print $name;print "Hello";

Can any one see a problem in this program ?

it runs!

(it should break)

$name is undefined

use strict;it breaks your program

in a nice way :-D

feature

Perl 5.10

← Perl6

use feature;

use feature ‘:5.10’

given - when - defaultgiven ($foo) { when (1) { say "\$foo == 1" } when ([2,3]) { say "\$foo == 2 || \$foo == 3" } when (/^a[bc]d$/) { say "\$foo eq 'abd' || \$foo eq 'acd'" } when ($_ > 100) { say "\$foo > 100" } default { say "None of the above" }}

state variables

sub counter { state $counts = 0; $counts += 1;}

say

say "hi";

print "hi\n";

say "hi";

use 5.010;

Perl6::*Perl6 functions implemented in Perl5

Perl6::Junctionsany, all

Q: How to test if an array contains a specific value ?

Does @arcontains 42 ?

$found = 0;foreach $a (@ar) { if ($a == 42) { $found = 1; last; }}if ($fount) { ...}

if ( grep { $_ == 42 } @ar ) { ...}

if ( grep /^42$/ @ar ) { ...}

use Perl6::Junction qw/ all any none one /;

if ( any(@ar) == 42 ) { ...}

if (all(@ar) > 42) { ...}

if (none(@ar) > 42) { ...}

if (one(@ar) > 42) { ...}

any(values %params) == undef

html form validation

any(@birthday) < str2time("1980/01/01")

if ( any(@a) == any(@b) ) { ...}

Can anyone see what it does now ?

Can anyone write a nested loop version in 10 seconds ?

• Perl6::Junction (any, all)

• Perl6::Perl

• Perl6::Builtins (system, caller)

• Perl6::Form

• Perl6::Gather

autobox

my $range = 10−>to(1);# => [ 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 ]

"Hello, world!"−>uc();# => "HELLO, WORLD!"

TryCatch first class try catch semantics

sub foo { eval { # some code that might die return "return value from foo"; } if ($@) { ... }}

sub foo { try { # some code that might die return "return value from foo"; } catch (Some::Error $e where { $_->code > 100 } ) { ... }}

Sub::Aliaseasier function alias

sub name { "gugod" }

alias get_name => 'name';alias getName => 'name';

selfmy $self = shift;

package MyClass;

sub myMethod { my $self = shift; ...}

package MyClass;use self;sub myMethod { ...}

Moose後現代的物件導向系統

Yet-anotherOO sub-system

EH?

¿ More ?

OF COURSE

Perl (5) is not like other Object Oriented Languages... does NOT have an OO built-in

That's why you should learn perl if you want to learn OO!

You can learn how to make an object system, not just how to use it.

Dan Kogai

package Point;use Moose;

has 'x' => (is => 'rw', isa => 'Int');has 'y' => (is => 'rw', isa => 'Int');

sub clear { my $self = shift; $self->x(0); $self->y(0);}

MooseX::Declare

class BankAccunt { has 'balance' => ( isa => 'Num', is => 'rw', default => 0 ); method deposit (Num $amount) { $self->balance( $self−>balance + $amount ); }

method withdraw (Num $amount) { my $current_balance = $self−>balance(); ( $current_balance >= $amount ) || confess "Account overdrawn"; $self->balance( $current_balance − $amount ); }}

Rubyish

package Cat;use Rubyish;

attr_accessor "name", "color";

def sound { "meow, meow" }

def speak { print "A cat goes " . $self−>sound . "\n";}

the evil perl

prototype

sub doMyWork { my ($arr1, $arr2) = @_; my @arr1 = @$arr1; my @arr2 = @$arr2; ...}

doMyWork(\@foo, \@bar);

sub doMyWork(\@\@) { my ($arr1, $arr2) = @_; my @arr1 = @$arr1; my @arr2 = @$arr2; ...}

doMyWork(@foo, @bar);

if (many { $_ > 50 } @arr) { ....}

sub many(&@) { my ($test_sub, @arr) = @_; ...}

AUTOLOAD

sub AUTOLOAD { my $program = $AUTOLOAD; $program =~ s/.*:://; system($program, @_);}date();who('am', 'i');ls('−l');

Source Filter

package BANG;use Filter::Simple; FILTER { s/BANG\s+BANG!!!/die 'BANG' if \$BANG/g;};

1;

use Acme::Morse;.--.-..--..---.-.--..--.-..--..---.-.--..-.-........---..-..---.-..-.--..---.--...-.---......-...-...-..--..-.-.-.--.-..----..-.-.--.-..--..-.-...---.-..---.--..-...-..--.---...-.-....

Module::Compile

DBinheritable built-in debugger

# from self.pmsub _args { my $level = 2; my @c = (); package DB; @c = caller($level++) while !defined($c[3]) || $c[3] eq '(eval)'; return @DB::args;}

PadWalkerruntime stack traveler

sub inc_x { my $h = peek_my(1); ${ $h->{'$x'} }++;}

Bindingeasier padwalker

use Binding;sub inc_x { my $b = Binding->of_caller; $b->eval('$x + 1');}

sub two { my $x = 1; inc_x;}

Devel::Declarecompile-time magician

Compile timecode injection

• you define “declarator” keywords

• it let compiler stop at the keywords

• your code parse the current line in your way, maybe re-write it

• you re-place current line with the new version

• it resumes the compiler on the current line

How it works

def foo($arg1, $arg2) { ....}

def foo($arg1, $arg2) { ....}

def foo($arg1, $arg2) { ....}

sub foo { my ($arg1, $arg2) = @_;}

B::Hooks::*more compile time fun

the better perl

to extend perl

the perfect perl

the perfect language?

Perl6 is perfect

The most extendable programming language

• variables

• functions, methods

• operator overloading

• operators

• grammars / rules

• sub-language

Perl6 is many languages

Perl6 are many languages

Perl5 world

• B::Generate

• Source Filter

• Devel::Declare

Conclusion

Perl is like the Force. It has a light side, a dark side, and it holds the universe together.

Larry Wall

The EndThanks for listening