Video here: http://www.youtube.com/watch?v=7Qsic1xmPKs At SoundCloud we ask candidates to send us some code before inviting them in for interviews. Candidates can use whatever language they want, and over the past year we saw a massive rise on the number of submissions using server-side JavaScript. Unfortunately, too many submissions are asynchronous blobs of procedural code. Let's talk about how to leverage good old Functional Programming techniques to make code less coupled and more readable! — https://secure.trifork.com/cph-2012/freeevent/index.jsp?eventOID=4353

1. Function Composition:
The top reason node.js
submissions get rejected by
SoundCloud
Phil Calçado - SoundCloud
@pcalcado
http://philcalcado.com
Friday, May 11, 12

2. ohai!
i’m phil.
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3. i work here:
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4. Friday, May 11, 12

5. and we are hiring.
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6. http://bit.ly/work-at-soundcloud
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7. Phone
Code Review
Interviews
Offer
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8. Phone
Code Review
Interviews
Offer
Friday, May 11, 12

9. you can choose any language.
% of submissions on the past ~6 months
40
30
20
10
0
Ruby Java JavaScript (Node.js) C Clojure Scala
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10. you can choose any language.
rejected before interview invited for inverview
40
30
20
10
0
Ruby Java JavaScript (Node.js) C Clojure Scala
Friday, May 11, 12

11. you can choose any language.
rejected before interview invited for inverview
40
WTF?
30
20
10
0
Ruby Java JavaScript (Node.js) C Clojure Scala
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12. we are all hipsters
http://bit.ly/J1aLNn
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13. Friday, May 11, 12

14. Not OO, not Functional...
Just (bad) Procedural code.
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15. http://bit.ly/JiECRp
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16. we don’t need this complicated stuff.
this is not java, you know.
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17. so what do we need?
http://bit.ly/JiFSnq
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18. http://bit.ly/JFbZt8
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19. “SICP and some of the Sussman & Steele "Lambda
the ..." papers made a big impression on me years
before, although I did not understand their full
meaning then.
Remember, I was recruited to "do Scheme" [...] My
interest in languages such as Self informed a
subversive agenda [...]. Likewise with first-class
functions, which were inspired by Scheme [...]”
http://bit.ly/JFbZt8
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20. http://bit.ly/JiEQYM
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27. going old school
http://bit.ly/JiF7ef
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28. e.g. passing functions around
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29. we see a lot of this
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30. 1st, we extract what is common
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31. then we refactor our functions
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32. and we send them as arguments
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33. e.g. closures not only for objects
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34. we see a lot of this
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35. we can keep writeComment as it is
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36. and we add a function with two closures
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37. and we add a function with two closures
immutable
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38. and we add a function with two closures
mutable immutable
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39. now we don’t need to pass in the kitchen sink
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40. e.g. functions all the way down
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41. we see a lot of this
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42. first we extract common protocol
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43. then we clean up our functions
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44. then we use them.
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45. then we use them. redundant?
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46. there is plenty to learn from.
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47. http://bit.ly/JiETnd
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48. Friday, May 11, 12

49. Qs?
Phil Calçado - SoundCloud
@pcalcado
http://philcalcado.com
Friday, May 11, 12

50. http://bit.ly/work-at-soundcloud
Friday, May 11, 12

51. How to Design Programs - http://bit.ly/K0BfrL
Structure and Interpretation of Computer
Programs - http://bit.ly/K0BjYm
The Art of the Metaobject Protocol
http://amzn.to/K0BqU1
Purely Functional Data Structures
http://amzn.to/JFn4KG
Let Over Lambda - http://amzn.to/IMMkNO
An Introduction to Lambda Calculi for Computer
Scientists - http://amzn.to/IX8d1B
All drawings are available as t-shirts from the
awesome Diesel Sweeties -
http://dieselsweeties.com/
Friday, May 11, 12