1.
It was finally Christmas:
Perl 6 is here!
Wim Vanderbauwhede
School of Compu6ng Science
University of Glasgow

2.
“Language is
ideology”
Kress, Gunther, et al. "Language as ideology." (1982).

3.
A trip down memory lane

4.
2007

5.
• Perl6/Pugs invited talk at POPL 2007
• Audrey Tang had created Pugs, a Perl 6
implementa6on in Haskell
• Perl 6 was promised for "Christmas”
• And there was some delay …

6.
Perl 6meline
Dow Jones index, 1985-2015

7.
Context
hZp://www.codeeval.com/

8.
Context
TIOBE Index for February 2016, hZp://www.6obe.com/
Popularity of programming languages – TIOBE

9.
Context
TIOBE Index for February 2016, hZp://www.6obe.com/
Popularity of programming languages – TIOBE

10.
Perl
Neil Stephenson, “Cryptonomicon”, p480

11.
Perl 5
• Interpreted
• Dynamically typed
• Garbage collec6on
• In that sense very similar to JavaScript,
Python, Ruby, …

12.
Perl 5
• Uses funny characters for typing:
$: scalar
@: array (list)
%: hash (dic6onary, map)
&: subrou6ne
• Incorporates a separate language:
regular expressions (PCRE)

13.
Perl 5
• But also:
• Lexical scoping
• Higher-order func6ons
• Anonymous func6ons
• Closures

14.
Perl 6
• Is a new language, not backward
compa6ble with Perl 5.
• S6ll mostly Perl
• But a modern language

15.
Compiler and VM

16.
Compiler (Rakudo)
hZps://github.com/rakudo/rakudo

17.
VM (MoarVM)
• Meta-object protocol based
• Precise, genera6onal, and parallel GC
• First-class code objects, closures, …
• Excep6ons
• Con6nua6ons
• Threads, mutexes, …
• JIT compila6on
hZps://github.com/MoarVM/MoarVM

18.
Grammars

19.
Parsing
• Perl 6 has Grammars, Rules, Tokens and Regexes as
part of the language
• Similar to classes but used to organize parsers
• Rules are lexeme parsers
• Tokens are token parsers
• Regexes are PCREs
• Perl 6 is parsed and executed using a Perl 6-style
grammar.

20.
Objects

21.
JavaScript Python
Objects

22.
Perl 6 Objects

23.
Perl 6 Objects
Roles

24.
Perl 6 Objects
• Accessors for free
• Default constructor
• Inheritance
• Roles (mixins)
• Built on a Meta Object Protocol
• Full introspec6on
• So s6ll nothing special …

25.
But wait …

26.
Perl 6 Objects

27.
Perl 6 Objects

28.
Gradual typing!

29.
Gradual typing
• By default variables are dynamically typed.
• Explicitly typed variables are sta6cally typed.
• But type checks can be deferred to run 6me.
• Underlying theory:
hZps://github.com/samth/gradual-typing-bib

30.
Gradual typing: subsets
• Type constraint checked at run 6me

31.
Gradual typing: type capture
• Defer the specifica6on of a type constraint to the
6me the func6on is called.
• Allows to refer to a type both in the signature and
the func6on body.

32.
Gradual typing: type capture
• Defer the specifica6on of a type constraint to the
6me the func6on is called.
• Allows to refer to a type both in the signature and
the func6on body.

33.
Roles

34.
Roles
• Basis for the Perl 6 type system
• Used for composi6on and mixins
• In Perl 6, the “funny characters” are syntax for a set
of predefined roles:
@: Posi6onal (array)
%: Associa6ve (hash)
&: Callable (subrou6ne)
• So …

35.
No more funny characters!
• Actually, the “funny characters” are now op6onal:

36.
Polymorphic func6ons
• Also known as mul6ple dispatch

37.
Polymorphic func6ons
• Also known as mul6ple dispatch

38.
Polymorphic func6ons
• Looks familiar?

39.
Parametric roles
• Roles that take one or more type variables

40.
Possibly Maybe

41.
FuncHonal
programming

42.
Func6onal features
• Higher-order func6ons
• Anonymous func6ons (lambdas)
• Currying
• Immutable lists, lazy evalua6on
• Tail call op6miza6on
• Op6onal immutable variables

43.
Type capture revisited
• Type capture also works with closures and lambdas

44.
Lazy lists
• Perl 6 dis6nguishes between sequences, lists and
arrays.
• Sequences are immutable, but are consumed
when iterated.
• Lists are immutable
• Arrays are mutable
• By defaults Seq, List and Array are lazy, but can be
made eager.

45.
Seq and List

46.
Array

47.
Promises

48.
Concurrency
• High-level
• Promises (futures)
• Channels
• Supplies
• Low-level
• Threads
• Schedulers
• Locks

49.
Promises

50.
Conclusion
•

51.
Thank you!