Go Beyond Paradigms

Is Go object oriented without inheritance? It has closures, but is it functional? The modern approach to learning languages focuses on features, not paradigms. This talk names key language features, how they affect design and coding patterns, and shows in practice how features relate to idiomatic code.

Transcript

1. T h e o r y i n P r a c t i c e GO BEYOND PARADIGMS Is Go object-oriented? Is that a good question? Understand language features, use the right patterns. Luciano Ramalho @ramalhoorg
2. 2 Sometimes you need a blank template.
3. FLUENT PYTHON 3 5 stars at amazon.de Published in 9 languages: •Chinese (simplified) •Chinese (traditional) •English •French •Japanese •Korean •Polish •Brazilian Portuguese •Russian 2nd edition: late 2020
4. TECH REVIEWER OF THE BRAZILIAN EDITION OF GOPL GOPL:
 The Go Programming Language Donovan & Kernighan 4
5. WORKSHOP: INTRODUCING GO WITH TDD 5 https://tgo.li/wtm-tdd-go
6. EMPORIO CELESTIAL By Jorge Luis Borges 6
10. PARADIGMS Programming language categories 10
11. A GOOD SURVEY-STYLE TEXTBOOK Programming Language Pragmatics,
 4th edition (2015) Michael L. Scott 11
12. GCD ASM X86 Máximo divisor comum em assembly x86 (Scott, 2015) 12
13. GCD IN C, OCAML, PROLOG 13
14. GCD IN GO Imperative style Functional style 14
15. GCD IN GO Imperative style Functional style 15 Bad fit for Go:
 no tail-call optimisation
16. SCOTT’S CLASSIFICATION 16 Programming Language Pragmatics,
 4th edition (2015) Michael L. Scott
17. SCOTT’S CLASSIFICATION (ZOOM) 17
18. SCOTT’S CLASSIFICATION (ZOOM) 18 ???
19. ANOTHER BOOK Princípios de Linguagens de Programação
 (2003) Ana Cristina Vieira de Melo Flávio Soares Corrêa da Silva 19
21. 21 Lógicas
22. THE GO FAMILY TREE 22 source:
 The Go Programming Language
 Donovan & Kernighan
23. CATEGORIES? Ontologies are so 1900’s 23
24. A CLASSIFICATION BASED ON HARD FACTS 24
25. A CLASSIFICATION BASED ON HARD FACTS 25 “Noble” gases!?
26. “Ontology is overrated.” Clay Shirky 26 https://tgo.li/onto-over
27. A BETTER APPROACH Fundamental Features of Programming Languages 27
28. HANDS-ON PROGRAMMING LANGUAGE THEORY 28
29. A PAPER PRESENTING THE APPROACH 29
30. A PAPER PRESENTING THE APPROACH 30
31. A PAPER PRESENTING THE APPROACH 31
32. A PAPER PRESENTING THE APPROACH 32
33. HANDS-ON WITH RACKET (A MODERN SCHEME DIALECT) 33
34. FEATURES Understand core features, not just syntax and libraries 34
35. SAMPLE FEATURES ✖ LANGUAGES 35 Common Lisp C Java Python Go First-class functions ✔ ∗ ✔ ✔ ✔ First-class types ✔ ✔ Iterators ∗ ✔ ✔ ∗ Variable model reference value* value and reference reference value* and reference Type checking dynamic static static dynamic static Type expression structural nominal nominal structural structural
36. SAMPLE FEATURES ✖ LANGUAGES 36 Common Lisp C Java Python Go First-class functions ✔ ∗ ✔ ✔ ✔ First class types ✔ ✔ Iterators ∗ ✔ ✔ ∗ Variable model reference value* value and reference reference value* and reference Type checking dynamic static static dynamic static Type expression structural nominal nominal structural structural Functions as objects Classes as objects
37. SAMPLE FEATURES ✖ LANGUAGES 37 Common Lisp C Java Python Go First-class functions ✔ ∗ ✔ ✔ ✔ First-class types ✔ ✔ Iterators ∗ ✔ ✔ ∗ Variable model reference value* value and reference reference value* and reference Type checking dynamic static static dynamic static Type expression structural nominal nominal structural structural
38. SAMPLE FEATURES ✖ LANGUAGES 38 Common Lisp C Java Python Go First-class functions ✔ ∗ ✔ ✔ ✔ First-class types ✔ ✔ Iterators ∗ ✔ ✔ ∗ Variable model reference value* value and reference reference value* and reference Type checking dynamic static static dynamic static Type expression structural nominal nominal structural structural
39. SAMPLE FEATURES ✖ LANGUAGES 39 Common Lisp C Java Python Go First-class functions ✔ ∗ ✔ ✔ ✔ First-class types ✔ ✔ Iterators ∗ ✔ ✔ ∗ Variable model reference value* value and reference reference value* and reference Type checking dynamic static static dynamic static Type expression structural nominal nominal structural structural
40. SAMPLE FEATURES ✖ LANGUAGES 40 Common Lisp C Java Python Go First-class functions ✔ ∗ ✔ ✔ ✔ First-class types ✔ ✔ Iterators ∗ ✔ ✔ ∗ Variable model reference value* value and reference reference value* and reference* Type checking dynamic static static dynamic static Type expression structural nominal nominal structural structural
41. DESIGN PATTERNS When languages fall short 41
42. GOF: CLASSIC BOOK BY THE “GANG OF FOUR” Design Patterns: Elements of Reusable Object-Oriented Software (1995) Erich Gamma
 Richard Helm
 Ralph Johnson
 John Vlissides 42
43. NOT EVERY PATTERN IS UNIVERSAL Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, Design Patterns: Elements of Reusable Object-Oriented Software (Addison-Wesley, 1995), p. 4. 43
44. NOT EVERY PATTERN IS UNIVERSAL Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, Design Patterns: Elements of Reusable Object-Oriented Software (Addison-Wesley, 1995), p. 4. 44
45. NOT EVERY PATTERN IS UNIVERSAL Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, Design Patterns: Elements of Reusable Object-Oriented Software (Addison-Wesley, 1995), p. 4. 45
49. ITERABLES & ITERATORS An excellent abstraction 49
50. ITERATION IN C 50 #include <stdio.h> int main(int argc, char *argv[]) { for(int i = 0; i < argc; i++) printf("%s\n", argv[i]); return 0; }
51. ITERATION IN GO 51
52. ITERATION IN C AND GO 52 #include <stdio.h> int main(int argc, char *argv[]) { for(int i = 0; i < argc; i++) printf("%s\n", argv[i]); return 0; }
53. FOREACH IN BARBARA LISKOV'S CLU 53 CLU Reference Manual — B. Liskov et. al. — © 1981 Springer-Verlag — also available online from MIT: http://publications.csail.mit.edu/lcs/pubs/pdf/MIT-LCS-TR-225.pdf © 2010 Kenneth C. Zirkel — CC-BY-SA
54. FOREACH IN CLU 54 year: 1975 CLU Reference Manual, p. 2 B. Liskov et. al. — © 1981 Springer-Verlag
55. ITERABLE OBJECTS: THE KEY TO FOREACH • Python, Java, CLU etc. let programmers define iterable objects
 
 
 
 
 
 
 • In Go, only array, slice, string, map, channel are supported by for/range 55 for item in an_iterable: process(item) for item in an_iterable: process(item)
56. ITERATOR PATTERN The classic recipe 56
57. THE ITERATOR FROM THE GANG OF FOUR Design Patterns
 Gamma, Helm, Johnson & Vlissides
 ©1994 Addison-Wesley 57
58. 58 Head First Design Patterns Poster
 O'Reilly
 ISBN 0-596-10214-3
59. CLASSIC
 ITERATOR IN GO The classic recipe in Go 59
60. USING A CLASSIC ITERATOR IN GO for/range not supported 60
61. IMPLEMENTING A CLASSIC ITERATOR IN GO Not too bad
 (if you like Java) 61
62. CHANNEL-BASED ITERATOR Leveraging Go features 62
63. for/range supported! USING A CHANNEL-BASED ITERATOR 63
64. USAGE COMPARISON 64
65. IMPLEMENTING A CHANNEL-BASED ITERATOR 65
66. IMPLEMENTATION COMPARISON 66
67. CONSIDERING THE OPTIONS A classic two-method iterator is more cumbersome to use and to implement. It is used in the standard library. Ex: buffio.Scanner (with methods called Scan and Text). Clients can quit at any time; iterator will be garbage-collected. A channel-based iterator is simpler to use and to implement. However, there is a context switch cost to run a coroutine, and the coroutine may leak if it does not run to completion. Allowing clients to cancel the iterator requires an additional channel for signaling. 67
68. STRATEGY IN GO Leveraging core features of Go 68
69. CHOOSE AN ALGORITHM AT RUN TIME 69
70. 70 Context Strategy Concrete strategies CHOOSE AN ALGORITHM AT RUN TIME
71. STRATEGY IN GO “Classic” implementation with an interface Implementation with first-class functions 71
72. TESTS 72 interface/strategy_test.go https://tgo.li/gobeyond2019
73. TESTS (CONT.) 73 interface/strategy_test.go https://tgo.li/gobeyond2019
74. CUSTOMER AND LINE ITEM 74 interface/store.go https://tgo.li/gobeyond2019
75. CONTEXT AND STRATEGY 75 interface/strategy.go https://tgo.li/gobeyond2019 Context Strategy
76. CONCRETE STRATEGY 76 interface/store.go https://tgo.li/gobeyond2019
77. MORE CONCRETE STRATEGIES 77 interface/store.go https://tgo.li/gobeyond2019
78. STRATEGY WITH FIRST CLASS FUNCTIONS 78
79. TESTS WITH FUNCTIONS 79
80. CONCRETE STRATEGIES AS FUNCTIONS 80
81. WHICH IS MORE IDIOMATIC GO? Interfaces v. Functions 81
82. WHICH IS MORE GOISH? Interfaces v. Functions 82
83. INTERFACES V. FIRST CLASS FUNCTIONS In the standard library, one-method interfaces are common. 83
84. INTERFACES V. FIRST CLASS FUNCTIONS But the http package supports both ways*: 84 *Kumar Iyer (ThoughtWorks): Higher-order functions vs interfaces in golang http://bit.ly/2j39uKh
85. WRAPPING UP Why learn the fundamentals 85
86. INSTEAD OF PARADIGMS… 86 A B C D E F G
87. FOCUS ON FUNDAMENTAL FEATURES 87 A B C D E F G
88. …to decide whether a particular pattern or implementation makes sense. FEATURES ARE THE BEST GUIDE… A B C D E F G + ✔ ✔ ✔ ✔ + ✔ ✔ ✔ ✔ + ✔ ✔ ✔ ✔ ✔
89. WHY LEARN THE FUNDAMENTALS* • Learn new languages more easily • Make the most of language features • Know how to choose alternative ways of implementation • Make good use of design patterns • Debug complicated bugs • Mimic useful features in languages where they are missing 89 Inspired by Programming Language Pragmatics Michael L. Scott *
90. Luciano Ramalho luciano.ramalho@thoughtworks.com
 Twitter: @ramalhoorg Github: https://github.com/standupdev Slides: speakerdeck.com/ramalho VIELEN DANK !