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Refactoring and Readability Southeast Linuxfest
 
 2019-06-14

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Refactoring and Readability http://speakerdeck.com/util
 
 <<< >>> >>> <<<

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OK, so we're doing this...
 


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


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OK, so we're doing this...
 -- Aaron Burr
 (Also)

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

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Refactoring and Readability http://speakerdeck.com/util
 
 <<< >>> >>> <<<

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Pump Up…

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Q&A ⅔

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/me

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Util

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RosettaCode:
 where Perl 6 goes to
 Flex Shine

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CodeFights 40 languages

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Assume Modern

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sub foo { die if @_ != 3; my ($x, $y, $z) = @_; ⋮ }

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# Assume all my Perl 5 code begins with: use strict; use warnings; use 5.020; use experimental qw;

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use strict; use warnings; use 5.020; use experimental qw; sub foo ( $x, $y, $z ) { ⋮

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use strict; use warnings; use 5.020; use experimental qw; sub foo ( $x, $y, $z ) { ⋮

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sub foo ( $x, $y, $z ) { ⋮

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last;

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Refactoring

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Refactoring Safely

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Refactoring Sanely

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git init
 git add .
 git commit -m 'Initial commit'

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sqlite + cUrl + perl + md5

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Modes Fix Add Refactor

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 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility (Slicing)

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 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility

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Mechanics

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sub final_form ($fighter) { ... code ... }

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sub trigger_final_form ($fighter) { ... code ... }

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sub final_form ($fighter) { return trigger_final_form($fighter); } sub trigger_final_form ($fighter) { ... code ... }

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sub trigger_final_form ($fighter) { ... code ... }

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Refactor to Debug:
 Wrapping

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sub should_log ( $department ) { my $r; if ( $audits{$department} ) { $r = 1 } elsif ( $department eq 'IA' ) { $r = 1 } else { $r = 0 } return $r; }

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sub should_log ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; }

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sub should_log ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; }

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sub should_log_WRAPPED ( $department ) { return 1 if $audits{$department}; return 1 if $department eq 'IA'; return 0; }

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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;

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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;

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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

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 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility

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 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility

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Rules Of Optimization wiki.c2.com First Rule Of Optimization - Don't. Second Rule Of Optimization - Don't... yet. Profile Before Optimizing

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That's another show...

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 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance (Speed) Boundaries of Responsibility

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Readability

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Readability

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Wholesale (changes)

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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 );

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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 );

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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 );

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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 );

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$machine->print( $format, $start ); $machine->reset( $init_value ); $machine->confuse( $level, $ray ); $register->print( $register ); $register->reset( $register ); $register->amend( $register, $new_value );

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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 );

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print_machine( $machine, $format, $start );

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print_machine( $machine, $format, $start );

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print_machine( $machine, $format, $start ); $machine->print( $format, $start );

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Dense

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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 ]++; }

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for my $car (@vehicles) { my $color = get_car_color(@car); $car->assemble_paint_and_ship($color); $dealers->give_credit_for_order($car); }

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Wow!

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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

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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

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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

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def factorial(n): fact = [ 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 6227020800, 87178291200, 1307674368000] return fact[n]

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def factorial(n): f = 1 for x in range(2, n+1): f *= x return f

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@factorials = 1, |[\*] 1 .. *; # Perl 6

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@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]

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def factorial(n): f = 1 for x in range(2, n+1): f *= x return f

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import math factorial = math.factorial

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Can't miss

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http://www.smbc-comics.com/comic/2010-11-26

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Enter the Matrix Final Chapter

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foo(); bar(); foo(); bar(); foo(); bar(); foo(); bar();

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for (1 .. 4) { foo(); bar(); }

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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

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[ 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 ],

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[ 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 ],

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[ 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 ],

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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] ⋮

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k = i + argmax( m[i:n], i )

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def argmax(m,i): col = [abs(row[i]) for row in m] return col.index(max(col))

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def argmax(m,i): col = [abs(row[i]) for row in m] return col.index(max(col))

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def argmax(m,i): col = [abs(row[i]) for row in m] return col.index(max(col)) # Double work!

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# Perl 5 use List::UtilsBy qw; $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);

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max( range(i, n), key = lambda x: abs(m[x][i]) )

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max( range(i, n), key = lambda x: abs(m[x][i]) )

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k = i + argmax( m[i:n], i ) k = max(range(i, n), key = lambda x: abs(m[x][i]))

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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

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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)

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Perl 6 == 
 Perl 5 minus Warts plus Awesome

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Thanks!

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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

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Copyrights

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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/


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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/

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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

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History • v 0.99 2019-06-06
 Presented at Atlanta Perlmongers (shelved) • v 1.01 2019-06-14
 Presented at Southeast LinuxFest