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Refactoring and Readability OSCON
 
 2019-07-17
 
 ( For coders, or coders-to-be )

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

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

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Q&A ==>

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/me

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Util

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Perl 6

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Can we agree
 that duels are dumb
 and immature?

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Can we agree
 that duels are dumb
 and immature? Sure!

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Can we agree
 that duels are dumb
 and immature? -- Aaron Burr Sure! -- Alexander Hamilton

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RosettaCode.org

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CodeFights 40 languages

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last;

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• Algorithms • Data structures • Patterns • Idiomatic coding • Code smells • Automated Testing • Commit workflow • Coding standards • Hiring • Language selection • API design • Theory of Programming Languages

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Refactoring

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Refactoring Safely

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Refactoring Safely 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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Modes Fix Add Refactor

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Force

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

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 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)

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 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)

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 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)

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 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)

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 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)

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 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)

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

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 Forces Surrounding Code Code 
 Inertia
 Respect
 Fear Easy to write Standard form Ease of change Easy to read Performance Boundaries of Responsibility

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

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Word

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// Array `packed` is ["hat", "glasses"]

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// Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks';

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// Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks');

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// Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks'); # Array `packed` is ['hat', 'glasses', 'socks']

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// Array `packed` is ["hat", "glasses"] packed[packed.length] = 'socks'; packed.push('socks'); # Array `packed` is ['hat', 'glasses', 'socks'] last_one = packed[-1]

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// 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]

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// 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]

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// 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()

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Don't
 Repeat
 Yourself

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// 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()

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 Forces Surrounding Code Code Easy to write Standard form
 (Pattern, Idiom, Standards, Vocab) Ease of change Easy to read Performance Boundaries of Responsibility

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


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


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https://docs.python.org/3/reference/
 https://docs.python.org/3/library/
 string
 itertools
 etc

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my $suspect; for my $p (@people) { if ( $p =~ /sketchy/ ) { $suspect = $p; last; } }

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my $suspect; for my $p (@people) { if ( $p =~ /sketchy/ ) { $suspect = $p; last; } } use List::Util qw; my $suspect = first { /sketchy/ } @people;

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http://www.ecma-international.org/ecma-262/

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http://www.ecma-international.org/ecma-262/
 
 developer.mozilla.org/en-US/docs/Web/JavaScript

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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 ($fighter) { } sub trigger_final_form ($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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 Forces Surrounding Code Code Easy to write Standard form Ease of change Easy to read Performance Boundaries of Responsibility

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

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Readability

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What's in a name?

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for my $car ( sort @cars ) { }

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for my $car ( sort @cars ) { } my @sorted_cars = sort @cars; for my $car (@sorted_cars) { }

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seek_manxome() whiffle() burble() snicker-snack() galumph()

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# These seven lines are to slay the Jabberwock. seek_manxome() whiffle() burble() snicker-snack() galumph()

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# These seven lines are to slay the Jabberwock. seek_manxome() whiffle() burble() snicker-snack() galumph()

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sub slay-the-Jabberwock { seek_manxome() whiffle() burble() snicker-snack() galumph() } ... slay-the-Jabberwock();

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A good full Pipe

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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if ( $s->wants_change_of_station ) { push @transfers, $i; } }

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if ( $s->wants_change_of_station ) { push @transfers, $i; } }

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if ( $s->wants_change_of_station ) { push @transfers, $i; } }

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if ( $s->wants_change_of_station ) { push @transfers, $i; } }

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if ( $s->wants_change_of_station ) { push @transfers, $i; } }

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if ( $s->wants_change_of_station ) { push @transfers, $i; } }

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if ( $s->wants_change_of_station ) { push @transfers, $i; } }

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push @transfers, $i if $s->wants_change_of_station;

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my ( $promote, $medals, @transfers ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; if ( !$promote ) { $promote = $s; } }

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if ( !$promote ) { $promote = $s; }

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$promote = $s if !$promote;

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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; }

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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; }

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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; }

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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; }

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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; }

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my @transfers; for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; push @transfers, $i if $s->wants_change_of_station; }

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my @transfers; for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; push @transfers, $i if $s->wants_change_of_station; }

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my @transfers; for my $i ( keys @soldiers ) { push @transfers, $i if $soldiers[$i]->wants_change_of_station; }

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my @transfers; for my $i ( keys @soldiers ) { push @transfers, $i if $soldiers[$i]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; }

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } @target = grep { CONDITION } @source;

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { CONDITION } @source;

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { CONDITION } keys @soldiers;

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { CONDITION } keys @soldiers;

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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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);

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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);

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; for ( keys @soldiers ) { push @transfers, $_ if $soldiers[$_]->wants_change_of_station; } my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers; my @temp = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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my ( $promote, $medals ); for my $i ( keys @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }

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my ( $promote, $medals ); for my $i ( @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }

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my ( $promote, $medals ); for my $i ( @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }

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my ( $promote, $medals ); for my $s ( @soldiers ) { my $s = $soldiers[$i]; if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }

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my ( $promote, $medals ); for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }

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my ( $promote, $medals ); for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; $promote = $s if !$promote; } }

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my $medals; for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; } } my $promote; for my $s ( @soldiers ) { if ( $s->valor ) { $promote = $s if !$promote; } }

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my $medals; for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; } } my $promote; for my $s ( @soldiers ) { if ( $s->valor ) { $promote = $s if !$promote; } }

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use List::Util qw; my $medals; for my $s ( @soldiers ) { if ( $s->valor ) { $medals += 2; } } my $promote; for my $s ( @soldiers ) { if ( $s->valor ) { $promote = $s if !$promote; } }

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use List::Util qw; my $medals; for ( @soldiers ) { if ( $_->valor ) { $medals += 2; } } my $promote; for ( @soldiers ) { if ( $_->valor ) { $promote = $_ if !$promote; } }

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use List::Util qw; my $medals; for ( @soldiers ) { if ( $_->valor ) { $medals += 2; } } my $promote; for ( @soldiers ) { if ( $_->valor ) { $promote = $_ if !$promote; } }

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote; for ( @soldiers ) { if ( $_->valor ) { $promote = $_ if !$promote; } }

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers;

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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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; } }

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use List::Util qw; my $medals = sum map { $_->valor ? 2 : 0 } @soldiers; my $promote = first { $_->valor } @soldiers; my @transfers = grep { $soldiers[$_]->wants_change_of_station } keys @soldiers;

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use List::Util qw; 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

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

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

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Can't miss

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Really can't miss

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Rate today's session O’Reilly Events App Session page on conference website

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Q&A

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

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Thanks!

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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/ (email me for the original Apple Keynote .key file)

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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

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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.

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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
 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


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Removed
 (Not presented, 
 but maybe worth reading)

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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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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->reset(); $register->amend( $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->reset(); $register->amend( $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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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)) # 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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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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Perl 6 == 
 Perl 5 minus Warts plus Awesome