Refactoring and Readability

Refactoring is:

worth practicing as a discrete skill
bound to an implied value judgement of "better" code
best served with a separate commit workflow
unsafe without automated testing

Readability is:

crucial to code quality
best achieved by "switching hats" during refactoring
to be prioritized over premature optimization.
beneficial to more than just technical debt

Transcript

1. Refactoring and Readability Southeast Linuxfest
 
 2019-06-14
3. Refactoring and Readability http://speakerdeck.com/util
 
 <bruce.gray@acm.org> <<< >>> >>> <<<
4. OK, so we're doing this...
 

5. OK, so we're doing this...
 -- Aaron Burr

6. OK, so we're doing this...
 -- Aaron Burr
 (Also)
7. OK, so we're doing this...
 -- Aaron Burr
 -- Brock Sampson
8. ( This space intentionally left blank )
9. Refactoring and Readability http://speakerdeck.com/util
 
 <bruce.gray@acm.org> <<< >>> >>> <<<
10. Pump Up…
11. Q&A ⅔
12. /me
13. Util
14. RosettaCode:
 where Perl 6 goes to
 Flex Shine
15. CodeFights 40 languages
16. Assume Modern
17. sub foo { die if @_ != 3; my ($x, $y, $z) = @_; ⋮ }
18. # Assume all my Perl 5 code begins with: use strict; use warnings; use 5.020; use experimental qw<signatures>;
19. use strict; use warnings; use 5.020; use experimental qw<signatures>; sub foo ( $x, $y, $z ) { ⋮
20. use strict; use warnings; use 5.020; use experimental qw<signatures>; sub foo ( $x, $y, $z ) { ⋮
21. sub foo ( $x, $y, $z ) { ⋮
22. last;
23. Refactoring
25. Refactoring Safely
26. Refactoring Sanely
27. git init
 git add .
 git commit -m 'Initial commit'
28. sqlite + cUrl + perl + md5
29. Modes Fix Add Refactor
30. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility (Slicing)
31. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility
32. Mechanics
33. sub final_form ($fighter) { ... code ... }
34. sub trigger_final_form ($fighter) { ... code ... }
35. sub final_form ($fighter) { return trigger_final_form($fighter); } sub trigger_final_form ($fighter) { ... code ... }
36. sub trigger_final_form ($fighter) { ... code ... }
37. Refactor to Debug:
 Wrapping
38. sub should_log ( $department ) { my $r; if ( $audits{$department} ) { $r = 1 } elsif ( $department eq 'IA' ) { $r = 1 } else { $r = 0 } return $r; }
39. sub should_log ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; }
40. sub should_log ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; }
41. sub should_log_WRAPPED ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; }
42. 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;
43. 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;
44. 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; perl -d pgm c should_log n p $department n p $r $r = 0 c
45. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility
46. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility
47. Rules Of Optimization wiki.c2.com First Rule Of Optimization - Don't. Second Rule Of Optimization - Don't... yet. Profile Before Optimizing
48. That's another show...
49. 
 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility
50. Readability
51. Readability
52. Wholesale (changes)
53. 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 );
54. 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 );
55. 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 );
56. 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 );
57. $machine->print( $format, $start ); $machine->reset( $init_value ); $machine->confuse( $level, $ray ); $register->print( $register ); $register->reset( $register ); $register->amend( $register, $new_value );
58. 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 );
59. print_machine( $machine, $format, $start );
60. print_machine( $machine, $format, $start );
61. print_machine( $machine, $format, $start ); $machine->print( $format, $start );
62. Dense
63. 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 ]++; }
64. for my $car (@vehicles) { my $color = get_car_color(@car); $car->assemble_paint_and_ship($color); $dealers->give_credit_for_order($car); }
65. Wow!
66. 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
67. 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
68. 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
69. def factorial(n): fact = [ 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 6227020800, 87178291200, 1307674368000] return fact[n]
70. def factorial(n): f = 1 for x in range(2, n+1): f *= x return f
71. @factorials = 1, |[\*] 1 .. *; # Perl 6
72. @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]
73. def factorial(n): f = 1 for x in range(2, n+1): f *= x return f
74. import math factorial = math.factorial
75. Can't miss
76. http://www.smbc-comics.com/comic/2010-11-26
77. Enter the Matrix Final Chapter
78. foo(); bar(); foo(); bar(); foo(); bar(); foo(); bar();
79. for (1 .. 4) { foo(); bar(); }
80. 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
81. [ 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 ],
82. [ 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 ],
83. [ 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 ],
84. 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] ⋮
85. k = i + argmax( m[i:n], i )
86. def argmax(m,i): col = [abs(row[i]) for row in m] return col.index(max(col))
87. def argmax(m,i): col = [abs(row[i]) for row in m] return col.index(max(col))
88. def argmax(m,i): col = [abs(row[i]) for row in m] return col.index(max(col)) # Double work!
89. # 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);
90. max( range(i, n), key = lambda x: abs(m[x][i]) )
91. max( range(i, n), key = lambda x: abs(m[x][i]) )
92. k = i + argmax( m[i:n], i ) k = max(range(i, n), key = lambda x: abs(m[x][i]))
93. 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
94. 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)
95. Perl 6 == 
 Perl 5 minus Warts plus Awesome
96. Thanks!
97. 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
98. Copyrights
99. 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/

100. 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/
101. Links • The original book, for Java. Now also for Ruby and JS
 https://refactoring.com/ • Book: Refactoring JavaScript
 http://refactoringjs.com/ • http://wiki.c2.com/?RulesOfOptimization • http://wiki.c2.com/?ProfileBeforeOptimizing
102. History • v 0.99 2019-06-06
 Presented at Atlanta Perlmongers (shelved) • v 1.01 2019-06-14
 Presented at Southeast LinuxFest