Know Your Types

GoRuCo 2014

Transcript

1. Know Your Types Michael R. Bernstein June 2014 Gotham Ruby Conference, NYC w michaelrbernste.in t @mrb_bk
2. I’m Obsessed
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
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
15. “A collection of type rules for a typed programming language. Same as static type system.” Type System
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
25. Isomorphism
26. iso morph
27. equal shape
28. Propositions are Types
30. Proofs are Programs
31. Normalization of proofs is evaluation of programs
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
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.”
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.”
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