Types As Premature Optimization

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Types @brixen As Premature Optimization

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Summary

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We can't use them well

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We usually don't need them

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They can harm more than help

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Questions?

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Under-specified What if we put the bread on the ﬂoor?

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Imperative Did we just use temporal coupling?

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Mutable state How will we know what's in the fridge?

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Repetitive Never heard of DRY?

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let a = bread! get a from breadbox! ...! spread b on a!

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Not abstract How are we going to scale?

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sandwich(:wheat,! :peanut_butter,! :jelly)

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sandwich(:rye,! :ham,! :swiss)

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*LTR Purely functional peanut butter & jelly sandwich (Extra credit: use static typing)

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General purpose

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Project failure KPMG (New Zealand) - Dec 2010 70% Had project failure in previous 12 months

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Project failure McKinsey & Company in conjunction with the University of Oxford - 2012 Failure could threaten company 17%

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0 25 50 75 100 Agile Traditional 67 73 Project success Dr Dobbs Journal - Aug 2007, Oct 2011

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We don't learn from failure

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We learn from other's failure

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Programming is a behavioral science Sorry maths people

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Perception Is it reality?

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Cognition Is it reality?

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3 8

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8 3

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3 8

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3 8

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if even then red

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if red then even Converse

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if red then even Converse

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if ¬even then ¬red Inverse

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if ¬even then ¬red Inverse

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if ¬red then ¬even Contrapositive

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3 8

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People who gave incorrect response 90%

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Propositions as types

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Statisticians

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Correct by construction

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We can't use them well

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Eight fallacies of programming

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Same scale 1

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klocs

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Same risk 2

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Same cost 3

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N * klocs = $

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Same granularity 4

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Everything is an object

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Everything is a function

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Same abstraction 5

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Same temporality 6

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Compile at one point in time

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Same order 7

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z → z2 + c

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They can harm more than help

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General purpose 8

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! nil!

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nil is not null

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! $ nil.to_s! => ""!

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! $ nil.to_h! => {}!

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! $ nil.to_i! => 0!

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! $ nil.to_c! => (0+0i)!

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id x = x

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f(g(h(x)))

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f(g(h(nil))) = nil

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class NilClass! def method_missing(*)! self! end! end

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We usually don't need them

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! puts "Hello, Barcelona!"!

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module Kernel! def puts(*args)! # ...! end! ! module_function :puts! end

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! puts "Hello, Barcelona!"!

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fun puts(*args)! # ...! end

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destroyallsoftware.com

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fun add(a, b)! a + b! end

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fun add(a: int, b: int)! a + b! end

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load_int 0, r1! load_int 1, r2! add r1, r2, r3! # ^a ^b ^c! store_int r3, 2

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CLIs

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parsers JSON • YAML • XML/HTML

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HTTP parsers

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Garbage collectors

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General purpose

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grammar date do! ...! end

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a = q r!

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Try Rubinius github.com/rubinius/rubinius

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# Gemfile! platforms :mri do! gem "ruby-debug"! end!

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$ bundle update

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$ bundle exec puma

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~2.1

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1.8.7

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Open source is not a spectator sport

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Don't worry, have fun

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"Don't worry about people stealing your ideas...

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"If your ideas are any good, you'll have to ram them down people's throats. —Howard H. Aiken

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"Sometimes the questions are complicated and the answers are simple" —Dr. Seuss

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"You never change things by fighting the existing reality...

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"To change something, build a new model that makes the existing model obsolete." —Buckminster Fuller

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"No [corporation] can stop an idea whose time has come. —Victor Hugo

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"Complain about the way other people make software by making software." —Andre Torrez

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@brixen

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Thank you!

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• Chaos: Making a New Science, James Gleick • The Power of Noticing: What the Best Leaders See, Max Bazerman • Smartcuts: How Hackers, Innovators, and Icons Accelerate Success, Shane Snow • You Are Not So Smart, David McRaney • You Are Now Less Dumb, David McRaney • Research Methods: The Basics, Nicholas Walliman • The Art of Thinking Clearly, Rolf Dobelli • Thinking, Fast and Slow, Daniel Kahneman • Intertwingled: Information Changes Everything, Peter Morville • https://en.wikipedia.org/wiki/Cyneﬁn • http://calleam.com/WTPF/?page_id=1445 References

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• http://commons.wikimedia.org/wiki/File:Peanut-Butter-Jelly-Sandwich.png • https://c1.staticﬂickr.com/5/4030/4695047698_9fd2da8a9f_z.jpg • http://www.teacher-chef.com/wp-content/uploads/2013/03/3-2013-peanut-butter.jpg • http://upload.wikimedia.org/wikipedia/commons/f/f6/Marmite_thick_spread_toasted_bread.jpg • http://farm3.staticﬂickr.com/2661/3725885335_61ef015d61_b.jpg • http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Peanut_butter_and_jelly_sandwich.jpg/ 1024px-Peanut_butter_and_jelly_sandwich.jpg • https://en.wikipedia.org/wiki/Oracle_OpenWorld • http://upload.wikimedia.org/wikipedia/commons/8/86/Ever_Given_container_ship.jpg • http://www.kenrockwell.com/trips/2010-05-nyc/6-01/IMG_7652-po-boxes.jpg • http://clubs1.bg/images/uploads/1237936572timo-glock-driving-with-toyota-hilux-stunt-team-in- melbourne_2.jpg • http://aviewfrommyseat.com/photos/newsmatt-20130923094556.jpg • http://upload.wikimedia.org/wikipedia/commons/1/15/Zombie_costume_portrait.jpg • http://upload.wikimedia.org/wikipedia/commons/d/de/Mandelbrot_set_rainbow_colors.png • http://4.bp.blogspot.com/_GvajRDbRRO4/TLmBW9Kdq5I/AAAAAAAAAp4/q6lyHTE1AuE/s1600/ Mandel_zoom_11_satellite_double_spiral.jpg • http://paulbourke.net/fractals/lorenz/lorenz4.png • http://upload.wikimedia.org/wikipedia/commons/3/39/MashedPotatoes.jpg • http://pixabay.com/static/uploads/photo/2013/03/29/16/27/book-97709_640.jpg Credits