Alejandro Marcu gave a presentation on programming in Hack. He began with his background in programming languages over the years. He then discussed Hack, noting that it started as a strict mode for PHP in 2012 and is now the only language that can be executed with HHVM. He covered key Hack features like types, collections, async, XHP for generating HTML, and code generation capabilities. He concluded with information on learning resources for Hack.

1. Programming in Hack
Alejandro Marcu
Dutch PHP Conference 2016

2. 2
 Started programming Logo at
8 years old
 Then moved to Basic, Turbo
Pascal, C++, Java
 2001 – 2004 Various
programming jobs in
Argentina
 2004 – 2008: TopCoder
 2009 – 2015: Facebook
Alejandro Marcu

3. 3
1. Introduction
2. Hack Types
3. Collections
4. Async
5. XHP
6. Hack Codegen
What You Will Learn Today

4. Introduction

5. 5
HHVM history
 2007 - Hackathon project: convert PHP to c++
 2009 – HipHop (HPHPc) in prod in Facebook
 2010 – Open sourced HipHop for PHP
 2010 – Started the HHVM project
 2013 – HHVM in prod in Facebook
 2013 – HHVM open sourced

6. 6
 In 2014 Wikipedia migrated to HHVM:
 CPU load went from 50% to 10%
 Mean page save time went 6s to 3s
 Average page load time went from 1.3s to 0.9s
 PHP 7 performance is close to HHVM
Example of migration to HHVM

7. 7
 Started in 2012 as “strict-mode” project
 Grew to be much more than that
 Open sourced in 2014
 As of now, HHVM is the only execution engine that
runs Hack
 Totally interoperable with PHP, allowing for a gradual
migration
Hack

8. 8
 Analyzes Hack programs statically
 Monitors files changes in the background
 Extremely fast, even in huge code bases
 Can even be used by IDEs to autocomplete code
Typechecker

9. Typechecker
hacklang.org/tutorial/

10. 10
 Type annotations
 Collections
 Async
 XHP
 Attributes
 Constructor parameter
Promotion
 Enums
 Generics
Hack only features
 Operators
 Lambda
 Null safe
 XHP attribute access
 Pipe operator
 Shapes
 Trait and interfaces
requirements
 Type aliases

11. 11
 References
 Global statements
 Top level code
 Variable variables
 Dynamic properties
 Pseudo-functions
 isset
 empty
 Unset
 goto
 Etc..
Unsupported features in Hack

12. 12
<?hh //strict  Type annotations required
 Can’t call PHP
 No top level code
 No references
<?hh // partial
or
<?hh
 The following is allowed but not checked:
• Calls to PHP
• Top level code
• References
 Type annotations not required but checked
if present
<?hh // decl  Not checked at all
 Functions and classes are indexed
 Use it only as the first step to migrate to
Hack
Typechecker modes

13. Type annotations

14. 14
Types
 Primitive types
 bool
 int
 float
 string
 array
 resource
 Combined primitive types
 num (int or float)
 arraykey (int or string)
 Object types
 Name of classes or interfaces

15. Return types
void can be used only as a return type

16. Parameters

17. Nullable parameters

18. Local variables

19. Class attributes

20. Class attributes

21. Class attributes

22. Constructor argument promotion

23. Enums

24. Enums

25. Enums

26. Generics

27. Arrays with generics

28. Collections

29. Vector
0-indexed list
Map
Keys: int or str.
Values: anything
Set
Unique elements
Collections overview

30. Vector

31. Map

32. Set

33. Immutability

34. Immutability

35. Immutability

36. Async

37. 37
 Single thread blocking
 Single thread non-blocking
 Multithread
Threads

38. Single Thread blocking example

39. Single Thread blocking example

40. Single Thread blocking example

41. Async example

42. Async example

43. Async example

44. 44
 Use the keyword async before function
 The return type must be Awaitable<…>
 Call async from async using await
 Call async from non-async using HHAsiojoin
 Make parallel calls using helpers in HHAsio
(such as v,vm,m,mf, etc.)
Async

45. XHP

46. 46
What is XHP?
 XHP is used to generate HTML in PHP or Hack
 No templating
 No string concatenating
 Represent HTML as a tree of objects
 Familiar XML syntax
 Secure
 Strong validations
 Extensible

47. Hello World
composer.json
xhp.php

48. Hello World

49. Adding children

50. Custom class definition

51. Inheriting and transferring attributes

52. Async components

53. 53
XHP parser transforms it into regular Hack code:
 XHP class names are replaced:
 First char colon is replaced with xhp_
 Other colons are replaced with two underscores
 Hyphens are replaced with an underscore
 E.g. :ui:nav:header is replaced with
xhp_ui__nav__header
XHP internals

54. 54
 XHP tags are replaced with constructors. E.g.
will be replaced with:
XHP internals

55. Hack Codegen

56. 56
Why code generation?
 Code generation: writing code that writes code
 Higher level of abstraction
 Generate boilerplate code
 Generate code from almost static data in database
 Replace usage of __call

57. 57
 Easy to create files, functions, classes, methods,
arrays, collections, etc
 Support for partially generated files
 Files can be signed
 No string concatenation
 No need to indent or add spaces
 https://github.com/facebook/hack-codegen/
 Composer: require facebook/hack-codegen
Hack Codegen

58. Hack Codegen example

59. Hack Codegen example output

60. ORM code generation

61. ORM code generation

62. ORM code generation

63. ORM code generation

64. Learning Resources

65. 65
Learning resources
 http://hacklang.org/ : installation, tutorial, docs
 “Hack & HHVM” book

66. Contact Information
amarcu@gmail.com
/alejandro.marcu
/alejandromarcu
@AlejandroMarcu
/in/alejandromarcu