Know Your Types

Transcript

1. Know Your Types Michael R. Bernstein June 2014 Gotham Ruby

   Conference, NYC w michaelrbernste.in t @mrb_bk

2. I’m Obsessed

3. None

4. What Are Types?

5. “What we talk about when we talk about types” Benton,

   2014

6. “We don't talk about types, we argue about them.”

7. “Type Systems” Cardelli, 1996

8. None

9. Computer Science Skill 0 25 50 75 100 Homepage Design

   Outdatedness Computer Science Skill vs. Homepage Design Outdatedness

10. Computer Science Skill 0 25 50 75 100 Homepage Design

    Outdatedness Bernstein’s Law

11. “A collection of values. An estimate of the collection of

    values that a program fragment can assume during program execution.” Type

12. int bool string int -> bool

13. “A component of a type system. A rule stating the

    conditions under which a particular program construct will not cause forbidden errors.” Type Rule
14. None

15. “A collection of type rules for a typed programming language.

    Same as static type system.” Type System
16. None

17. “A language where good behavior is determined before execution.” Statically

    checked language

18. “A language where good behavior is enforced during execution.” Dynamically

    checked language

19. “The process of checking a program before execution to establish

    its compliance with a given type system and therefore to prevent the occurrence of forbidden errors.” Typechecking

20. “The process of finding a type for a program within

    a given type system.” Type Inference

21. How Can Types Help Us?

22. “Propositions as Types” Wadler, 2014

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25. Isomorphism

26. iso morph

27. equal shape

28. Propositions are Types

29. None

30. Proofs are Programs

31. Normalization of proofs is evaluation of programs

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37. Deep Understanding

38. Mathematical Certainty

39. Enlightenment

40. “Types and Programming Languages” a.k.a ‘TAPL’ Pierce, 2002

41. Detecting Errors

42. Abstraction

43. Documentation

44. Safety

45. So Much More!

46. Types and Ruby (But Really Dynamic Languages in General)

47. “A Practical Optional Type System for Clojure” Bonnaire-Sergeant,2012

48. None

49. “Typed Scheme: From Scripts to Programs” Tobin-Hochstadt, 2010

50. “Gradual Typing for Functional Languages” Siek & Taha, 2006

51. Gradual Typing

52. “…safe interoperability between typed and untyped portions of a single

    program” ! - Sam Tobin-Hochstadt

53. “Dynamic Inference of Static Types for Ruby” An, Chaudhuri, Foster,

    Hicks, 2011

54. “…constraint-based dynamic type inference, a technique that infers static types

    based on dynamic program executions.”
55. None

56. “The Ruby Type Checker” Ren, Toman, Strickland, Foster 2013

57. “RTC is designed so programmers can control exactly where type

    checking occurs: type-annotated objects serve as the “roots” of the type checking process, and unan- notated objects are not type checked.”
58. None

59. Challenges

60. “Experience from Developing the Dialyzer: A Static Analysis Tool Detecting

    Defects in Erlang Applications” Sagonas, 2005

61. “…testing, no matter how thorough, cannot of course detect all

    software defects. Tools that complement testing, such as static analyzers, have their place in software development regardless of language.”

62. Conclusions

63. Types and Type Systems Are Really, Really Cool

64. Types Are A Prism

65. A Type System Can Be A Guide

66. Let’s Push It Forward

67. Thank You w michaelrbernste.in t @mrb_bk