Refactoring and Readability - OSCON 2019

Quality literature isn’t produced by just writing; it’s in the rewriting that excellence is achieved. This is also true with code. Readability is crucial to code quality and is best achieved by switching your mind-set from writer to reader. That switch fits naturally into the act of refactoring.

Bruce Gray shines a spotlight on swapping hats, moving fluidly from problem solving (writer role) to communicating (editor role) and back. Refactoring is to programmers as lifting is to UPS workers: so basic that it gets overlooked, yet so fundamental that doing it naively can hurt. Refactoring is worth practicing as a discrete skill, bound to an implied value judgement of better code, best served with a separate commit workflow, and unsafe without automated testing.

Transcript

1. Refactoring and Readability OSCON
 
 2019-07-17
 
 ( For coders, or coders-to-be )
3. Refactoring and Readability http://speakerdeck.com/util
 
 <bruce.gray@acm.org> <<< >>> >>> <<<
4. ( This space intentionally left blank )
5. Refactoring and Readability http://speakerdeck.com/util
 
 <bruce.gray@acm.org> <<< >>> >>> <<<
6. Q&A ==>
7. /me
8. Util
9. Perl 6
10. Can we agree
 that duels are dumb
 and immature?
11. Can we agree
 that duels are dumb
 and immature? Sure!
12. Can we agree
 that duels are dumb
 and immature? -- Aaron Burr Sure! -- Alexander Hamilton
13. RosettaCode.org
14. CodeFights 40 languages
15. last;
16. • Algorithms • Data structures • Patterns • Idiomatic coding • Code smells • Automated Testing • Commit workflow • Coding standards • Hiring • Language selection • API design • Theory of Programming Languages
17. Refactoring
19. Refactoring Safely
20. Refactoring Safely Sanely
21. git init
 git add .
 git commit -m 'Initial commit'
22. sqlite + cUrl + perl + md5
23. Modes Fix Add Refactor
24. Modes Fix Add Refactor
25. Force
26. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance Boundaries of Responsibility
27. 
 Forces Surrounding Code (Context) Code Easy to write (hack hack hack) Standard form
 (Pattern, Idiom, Standards, Vocab) Ease of change (Flexibility) Easy to read (Time until comprehension ) Performance (Speed) Boundaries of Responsibility (Slicing)
28. 
 Forces Surrounding Code (Context) Code Easy to write (hack hack hack) Standard form
 (Pattern, Idiom, Standards, Vocab) Ease of change (Flexibility) Easy to read (Time until comprehension ) Performance (Speed) Boundaries of Responsibility (Slicing)
29. 
 Forces Surrounding Code (Context) Code Easy to write (hack hack hack) Standard form
 (Pattern, Idiom, Standards, Vocab) Ease of change (Flexibility) Easy to read (Time until comprehension ) Performance (Speed) Boundaries of Responsibility (Slicing)
30. 
 Forces Surrounding Code (Context) Code Easy to write (hack hack hack) Standard form
 (Pattern, Idiom, Standards, Vocab) Ease of change (Flexibility) Easy to read (Time until comprehension ) Performance (Speed) Boundaries of Responsibility (Slicing)
31. 
 Forces Surrounding Code (Context) Code Easy to write (hack hack hack) Standard form
 (Pattern, Idiom, Standards, Vocab) Ease of change (Flexibility) Easy to read (Time until comprehension ) Performance (Speed) Boundaries of Responsibility (Slicing)
32. 
 Forces Surrounding Code (Context) Code Easy to write (hack hack hack) Standard form
 (Pattern, Idiom, Standards, Vocab) Ease of change (Flexibility) Easy to read (Time until comprehensio n) Performance (Speed) Boundaries of Responsibility (Slicing)
33. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance Boundaries of Responsibility
34. 
 Forces Surrounding Code Code 
 Inertia
 Respect
 Fear Easy to write Standard form Ease of change Easy to read Performance Boundaries of Responsibility
35. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance Boundaries of Responsibility
36. Word
37. // Array `packed` is ["hat", "glasses"]
38. // Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks';
39. // Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks');
40. // Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks'); # Array `packed` is ['hat', 'glasses', 'socks']
41. // Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks'); # Array `packed` is ['hat', 'glasses', 'socks'] last_one = packed[-1]
42. // Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks'); # Array `packed` is ['hat', 'glasses', 'socks'] last_one = packed[-1] packed = packed[0:-1]
43. // Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks'); # Array `packed` is ['hat', 'glasses', 'socks'] last_one = packed[-1] packed = packed[0:-1]
44. // Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks'); # Array `packed` is ['hat', 'glasses', 'socks'] last_one = packed[-1] packed = packed[0:-1] last_one = packed.pop()
45. Don't
 Repeat
 Yourself
46. // Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks'); # Array `packed` is ['hat', 'glasses', 'socks'] last_one = packed[-1] packed = packed[0:-1] last_one = packed.pop()
47. 
 Forces Surrounding Code Code Easy to write Standard form
 (Pattern, Idiom, Standards, Vocab) Ease of change Easy to read Performance Boundaries of Responsibility
48. https://docs.python.org/3/reference/

49. https://docs.python.org/3/reference/
 https://docs.python.org/3/library/

50. https://docs.python.org/3/reference/
 https://docs.python.org/3/library/
 string
 itertools
 etc
51. my $suspect; for my $p (@people) { if ( $p =~ /sketchy/ ) { $suspect = $p; last; } }
52. my $suspect; for my $p (@people) { if ( $p =~ /sketchy/ ) { $suspect = $p; last; } } use List::Util qw<first>; my $suspect = first { /sketchy/ } @people;
53. http://www.ecma-international.org/ecma-262/
54. http://www.ecma-international.org/ecma-262/
 
 developer.mozilla.org/en-US/docs/Web/JavaScript
55. Mechanics
56. sub final_form ($fighter) { ... code ... }
57. sub trigger_final_form ($fighter) { ... code ... }
58. sub final_form ($fighter) { } sub trigger_final_form ($fighter) { ... code ... }
59. sub final_form ($fighter) { return trigger_final_form($fighter); } sub trigger_final_form ($fighter) { ... code ... }
60. sub trigger_final_form ($fighter) { ... code ... }
61. Refactor to Debug:
 Wrapping
62. sub should_log ( $department ) { my $r; if ( $audits{$department} ) { $r = 1 } elsif ( $department eq 'IA' ) { $r = 1 } else { $r = 0 } return $r; }
63. sub should_log ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; }
64. sub should_log ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; }
65. sub should_log_WRAPPED ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; }
66. sub should_log_WRAPPED ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; } sub should_log ( $department ) { my $r = should_log_WRAPPED($department); return $r;
67. sub should_log_WRAPPED ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; } sub should_log ( $department ) { say "> should_log:", Dumper $department; my $r = should_log_WRAPPED($department); say "< should_log:", Dumper $r; return $r;
68. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance Boundaries of Responsibility
69. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance Boundaries of Responsibility
70. Rules Of Optimization wiki.c2.com First Rule Of Optimization - Don't. Second Rule Of Optimization - Don't... yet. Profile Before Optimizing
71. That's another show...
72. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance Boundaries of Responsibility
73. Readability
74. What's in a name?
75. for my $car ( sort @cars ) { }
76. for my $car ( sort @cars ) { } my @sorted_cars = sort @cars; for my $car (@sorted_cars) { }
77. seek_manxome() whiffle() burble() snicker-snack() galumph()
78. # These seven lines are to slay the Jabberwock. seek_manxome() whiffle() burble() snicker-snack() galumph()
79. # These seven lines are to slay the Jabberwock. seek_manxome() whiffle() burble() snicker-snack() galumph()
80. sub slay-the-Jabberwock { seek_manxome() whiffle() burble() snicker-snack() galumph() } ... slay-the-Jabberwock();
81. A good full Pipe
83. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
84. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
85. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
86. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
87. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
88. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
89. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
90. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
91. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
92. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
93. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
94. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
95. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
96. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
97. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
98. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
99. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
100. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
101. if ( $s->wants_change_of_station ) { push @transfers, $i; } }
102. if ( $s->wants_change_of_station ) { push @transfers, $i; } }
103. if ( $s->wants_change_of_station ) { push @transfers, $i; } }
104. if ( $s->wants_change_of_station ) { push @transfers, $i; } }
105. if ( $s->wants_change_of_station ) { push @transfers, $i; } }
106. if ( $s->wants_change_of_station ) { push @transfers, $i; } }
107. if ( $s->wants_change_of_station ) { push @transfers, $i; } }
108. push @transfers, $i if $s->wants_change_of_station;
109. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }
110. if ( !$promote ) { $promote = $s; }
111. $promote = $s if !$promote;
112. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } push @transfers, $i if $s->wants_change_of_station; }
113. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } push @transfers, $i if $s->wants_change_of_station; }
114. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } } for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; push @transfers, $i if $s->wants_change_of_station; }
115. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } } for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; push @transfers, $i if $s->wants_change_of_station; }
116. my ( $promote, $medals ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } } my @transfers; for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; push @transfers, $i if $s->wants_change_of_station; }
117. my @transfers; for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; push @transfers, $i if $s->wants_change_of_station; }
118. my @transfers; for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; push @transfers, $i if $s->wants_change_of_station; }
119. my @transfers; for my $i ( keys @soldiers ) { push @transfers, $i if $soldiers[$i]->wants_change_of_station; }
120. my @transfers; for my $i ( keys @soldiers ) { push @transfers, $i if $soldiers[$i]->wants_change_of_station; }
121. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }
122. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }
123. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }
124. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }
125. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }
126. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }
127. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }
128. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }
129. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }
130. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } @target = grep { CONDITION } @source;
131. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { CONDITION } @source;
132. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { CONDITION } keys @soldiers;
133. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { CONDITION } keys @soldiers;
134. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
135. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers; die if join(',', @temp) ne join(',', @soldiers);
136. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers; log if join(',', @temp) ne join(',', @soldiers);
137. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
138. my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
139. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
140. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
141. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
142. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
143. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
144. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
145. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
146. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
147. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
148. my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
149. my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
150. my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
151. my ( $promote, $medals ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }
152. my ( $promote, $medals ); for my $i ( @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }
153. my ( $promote, $medals ); for my $i ( @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }
154. my ( $promote, $medals ); for my $s ( @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }
155. my ( $promote, $medals ); for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }
156. my ( $promote, $medals ); for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }
157. my $medals; for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; } } my $promote; for my $s ( @soldiers ) { if ( $s->valor ) { $promote = $s if !$promote; } }
158. my $medals; for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; } } my $promote; for my $s ( @soldiers ) { if ( $s->valor ) { $promote = $s if !$promote; } }
159. use List::Util qw<sum first>; my $medals; for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; } } my $promote; for my $s ( @soldiers ) { if ( $s->valor ) { $promote = $s if !$promote; } }
160. use List::Util qw<sum first>; my $medals; for ( @soldiers ) { if ( $_->valor ) { $medals += 2; } } my $promote; for ( @soldiers ) { if ( $_->valor ) { $promote = $_ if !$promote; } }
161. use List::Util qw<sum first>; my $medals; for ( @soldiers ) { if ( $_->valor ) { $medals += 2; } } my $promote; for ( @soldiers ) { if ( $_->valor ) { $promote = $_ if !$promote; } }
162. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote; for ( @soldiers ) { if ( $_->valor ) { $promote = $_ if !$promote; } }
163. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers;
164. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
165. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
166. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
167. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
168. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
169. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
170. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
171. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
172. my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } } if ( $s->wants_change_of_station ) { push @transfers, $i; } }
173. use List::Util qw<sum first>; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;
174. use List::Util qw<sum first>; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers; my @valor = grep { $_->valor } @soldiers; my $medals = 2 * @valor; my $promote = $valor[0]; # Version for people who cannot pause their performance obsession
175. Wow!
176. def factorial(n): n0 = 1 n1 = 1 n2 = 2 n3 = 6 n4 = 24 n5 = 120 n6 = 720 n7 = 5040 n8 = 40320 n9 = 362880 n10 = 3628800 n11 = 39916800 n12 = 479001600 n13 = 6227020800 n14 = 87178291200 n15 = 1307674368000 if n == 0: return n0 elif n == 1: return n1 elif n == 2: return n2 elif n == 3: return n3 elif n == 4: return n4 elif n == 5: return n5 elif n == 6: return n6 elif n == 7: return n7 elif n == 8: return n8 elif n == 9: return n9 elif n == 10: return n10 elif n == 11: return n11 elif n == 12: return n12 elif n == 13: return n13 elif n == 14: return n14 elif n == 15: return n15
177. def factorial(n): n0 = 1 n1 = 1 n2 = 2 n3 = 6 n4 = 24 n5 = 120 n6 = 720 n7 = 5040 n8 = 40320 n9 = 362880 n10 = 3628800 n11 = 39916800 n12 = 479001600 n13 = 6227020800 n14 = 87178291200 n15 = 1307674368000 if n == 0: return n0 elif n == 1: return n1 elif n == 2: return n2 elif n == 3: return n3 elif n == 4: return n4 elif n == 5: return n5 elif n == 6: return n6 elif n == 7: return n7 elif n == 8: return n8 elif n == 9: return n9 elif n == 10: return n10 elif n == 11: return n11 elif n == 12: return n12 elif n == 13: return n13 elif n == 14: return n14 elif n == 15: return n15
178. def factorial(n): if n == 0: return 1 elif n == 1: return 1 elif n == 2: return 2 elif n == 3: return 6 elif n == 4: return 24 elif n == 5: return 120 elif n == 6: return 720 elif n == 7: return 5040 elif n == 8: return 40320 elif n == 9: return 362880 elif n == 10: return 3628800 elif n == 11: return 39916800 elif n == 12: return 479001600 elif n == 13: return 6227020800 elif n == 14: return 87178291200 elif n == 15: return 1307674368000
179. def factorial(n): fact = [ 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 6227020800, 87178291200, 1307674368000] return fact[n]
180. def factorial(n): f = 1 for x in range(2, n+1): f *= x return f
181. @factorials = 1, |[\*] 1 .. *; # Perl 6
182. @factorials = 1, |[\*] 1 .. *; # Perl 6 fact = [1] # Caches between calls! def factorial(n): while len(fact)-1 < n: fact.append( fact[-1] * len(fact) ) return fact[n]
183. def factorial(n): f = 1 for x in range(2, n+1): f *= x return f
184. import math factorial = math.factorial
185. def factorial(n): f = 1 for x in range(2, n+1): f *= x return f
186. def factorial(n): n0 = 1 n1 = 1 n2 = 2 n3 = 6 n4 = 24 n5 = 120 n6 = 720 n7 = 5040 n8 = 40320 n9 = 362880 n10 = 3628800 n11 = 39916800 n12 = 479001600 n13 = 6227020800 n14 = 87178291200 n15 = 1307674368000 if n == 0: return n0 elif n == 1: return n1 elif n == 2: return n2 elif n == 3: return n3 elif n == 4: return n4 elif n == 5: return n5 elif n == 6: return n6 elif n == 7: return n7 elif n == 8: return n8 elif n == 9: return n9 elif n == 10: return n10 elif n == 11: return n11 elif n == 12: return n12 elif n == 13: return n13 elif n == 14: return n14 elif n == 15: return n15
187. def factorial(n): f = 1 for x in range(2, n+1): f *= x return f
188. Can't miss
189. Really can't miss
190. Rate today's session O’Reilly Events App Session page on conference website
191. Q&A
192. Refactoring and Readability http://speakerdeck.com/util
 
 <bruce.gray@acm.org> <<< >>> >>> <<<
193. Thanks!
194. Copyrights
195. Copyright Information: Images • Camelia • (c) 2009 by Larry Wall
 http://github.com/perl6/mu/raw/master/misc/ camelia.txt • New rules for Science Journalism • Zach Weinersmith
 http://www.smbc-comics.com/comic/ 2010-11-26 • Packages • © Randall Munroe
 https://xkcd.com/576/

196. Copyright Information: This Talk This work is licensed under a Creative Commons Attribution 4.0 International License. CC BY https://creativecommons.org/licenses/by/4.0/ (email me for the original Apple Keynote .key file)
197. Recommended Links • The original book, for Java. Now also for Ruby and JS
 https://refactoring.com/ • Book: Refactoring JavaScript. Worth learning JS just to read it!
 http://refactoringjs.com/ • The Art of Readable Code
 http://shop.oreilly.com/product/9780596802301.do • http://wiki.c2.com/?RulesOfOptimization • http://wiki.c2.com/?ProfileBeforeOptimizing
198. Anti-Links • None yet.
 If I did not list a relevant book in Links,
 it probably just means I have not read that book in depth yet.
199. History • v 0.99 2019-06-06
 Presented at Atlanta Perlmongers
 (shelved) • v 1.01 2019-06-14
 Presented at Southeast LinuxFest
 60 minutes with Q&A • v 1.02 2019-06-17
 Presented at The Perl Conference
 50 minutes with Q&A • v 1.03 2019-06-17
 Presented at OSCON, with many changes
 40 minutes with Q&A

200. Removed
 (Not presented, 
 but maybe worth reading)
201. Dense
202. for my $car (@vehicles) { my $color = $colors_by_type[ $car->type ]; if ( not $color->available ) { $color = $colors_by_type[ rand @colors_by_type ]; } $car->assemble_inspect_and_ship($color); $dealers[ $car->order_source ]++; }
203. for my $car (@vehicles) { my $color = get_car_color(@car); $car->assemble_paint_and_ship($color); $dealers->give_credit_for_order($car); }
204. Wholesale (changes)
205. print_machine( $machine, $format, $start ); reset_machine( $machine, $init_value ); confuse_machine( $machine, $level, $ray ); print_register( $register ); reset_register( $register ); amend_register( $register, $new_value );
206. print_machine( $machine, $format, $start ); reset_machine( $machine, $init_value ); confuse_machine( $machine, $level, $ray ); print_register( $register ); reset_register( $register ); amend_register( $register, $new_value );
207. print_machine( $machine, $format, $start ); reset_machine( $machine, $init_value ); confuse_machine( $machine, $level, $ray ); print_register( $register ); reset_register( $register ); amend_register( $register, $new_value );
208. print_machine( $machine, $format, $start ); reset_machine( $machine, $init_value ); confuse_machine( $machine, $level, $ray ); print_register( $register ); reset_register( $register ); amend_register( $register, $new_value );
209. $machine->print( $format, $start ); $machine->reset( $init_value ); $machine->confuse( $level, $ray ); $register->print(); $register->reset(); $register->amend( $new_value );
210. print_machine( $machine, $format, $start ); reset_machine( $machine, $init_value ); confuse_machine( $machine, $level, $ray ); print_register( $register ); reset_register( $register ); amend_register( $register, $new_value );
211. $machine->print( $format, $start ); $machine->reset( $init_value ); $machine->confuse( $level, $ray ); $register->print(); $register->reset(); $register->amend( $new_value );
212. print_machine( $machine, $format, $start ); reset_machine( $machine, $init_value ); confuse_machine( $machine, $level, $ray ); print_register( $register ); reset_register( $register ); amend_register( $register, $new_value );
213. print_machine( $machine, $format, $start );
214. print_machine( $machine, $format, $start );
215. print_machine( $machine, $format, $start ); $machine->print( $format, $start );
216. Enter the Matrix Final Chapter
217. foo(); bar(); foo(); bar(); foo(); bar(); foo(); bar();
218. for (1 .. 4) { foo(); bar(); }
219. 31w + 55x + 46y + 30z = 76 84w + 92x + 37y + 72z = 16 57w + 37x + 34y + 85z = 71 93w + 62x + 71y + 49z = 42 86w + 48x + 36y + 42z = 88 -34w + 71x + 47y + 32z = 73 21w + 32x + 34y + 19z = 54 -99w + 25x + 39y + 62z = 23
220. [ 1, 0, 0, 0, 31, 55, 46, 30, 76 ], [ 0, 1, 0, 0, 84, 92, 37, 72, 16 ], [ 0, 0, 1, 0, 57, 37, 34, 85, 71 ], [ 0, 0, 0, 1, 93, 62, 71, 49, 42 ], [ 0, 0, 0, 0, 86, 48, 36, 42, 88 ], [ 0, 0, 0, 0, -34, 71, 47, 32, 73 ], [ 0, 0, 0, 0, 21, 32, 34, 19, 54 ], [ 0, 0, 0, 0, -99, 25, 39, 62, 23 ],
221. [ 1, 0, 0, 0, 31, 55, 46, 30, 76 ], [ 0, 1, 0, 0, 84, 92, 37, 72, 16 ], [ 0, 0, 1, 0, 57, 37, 34, 85, 71 ], [ 0, 0, 0, 1, 93, 62, 71, 49, 42 ], [ 0, 0, 0, 0, 86, 48, 36, 42, 88 ], [ 0, 0, 0, 0, -34, 71, 47, 32, 73 ], [ 0, 0, 0, 0, 21, 32, 34, 19, 54 ], [ 0, 0, 0, 0, -99, 25, 39, 62, 23 ],
222. [ 1, 0, 0, 0, 31, 55, 46, 30, 76 ], [ 0, 1, 0, 0, 84, 92, 37, 72, 16 ], [ 0, 0, 1, 0, 57, 37, 34, 85, 71 ], [ 0, 0, 0, 1, 93, 62, 71, 49, 42 ], [ 0, 0, 0, 0, 86, 48, 36, 42, 88 ], [ 0, 0, 0, 0, -34, 71, 47, 32, 73 ], [ 0, 0, 0, 0, 21, 32, 34, 19, 54 ], [ 0, 0, 0, 0, -99, 25, 39, 62, 23 ],
223. def gauss(m): n, p = len(m), len(m[0]) for i in range(n): k = i + argmax(m[i:n],i) m[i], m[k] = m[k], m[i] ⋮
224. k = i + argmax( m[i:n], i )
225. def argmax(m,i): col = [abs(row[i]) for row in m] return col.index(max(col))
226. def argmax(m,i): col = [abs(row[i]) for row in m] return col.index(max(col)) # Double work!
227. # Perl 5 use List::UtilsBy qw<max_by>; $tallest = max_by { $_->height } @people; # Perl 6 $tallest = @people.max( *.height ); # Python (since 2.5 in 2006) tallest = max(people, key=lambda x: x.height);
228. max( range(i, n), key = lambda x: abs(m[x][i]) )
229. max( range(i, n), key = lambda x: abs(m[x][i]) )
230. k = i + argmax( m[i:n], i ) k = max(range(i, n), key = lambda x: abs(m[x][i]))
231. k = i + argmax( m[i:n], i ) k = max(range(i, n), key = lambda x: abs(m[x][i])) $k = max_by { abs($m[$_][$i]) } $i..$#m; #P5
232. def column_index_with_max_abs_value(m,i): return max(range(i, n), key = lambda x: abs(m[x][i])) k = column_index_with_max_abs_value(m,i)
233. Key knowledge (Perl) • List::Util first max min sum all any none uniq shuffle • List::UtilsBy max_by min_by count_by • perlfunc Perl Functions by Category • Test::Tutorial Intro to Automated Testing • Devel::Cover Shows code that lacks testing • Benchmark Performance comparisons • Devel::NYTProf Perfomance profiler
234. Perl 6 == 
 Perl 5 minus Warts plus Awesome