Rather than continually instructing a computer on how to get the job done, wouldn't it be so much easier if we simply had to explain what we wanted, and have the computer fill in the blanks for us? Functional programming gives us this ability through its focus and priority on functions, rather than variables and classes, which allows us to reduce coupling and complexity, giving us a more repeatable program. In this talk I'll explain my journey to understand, appreciate and leverage the power given to me by functional programming. See more at https://github.com/jamesottaway/decks

1. FUNCTIONAL
PROGRAMMING
function() {
return [‘fun’,‘profit’];
}
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2. James Ottaway
@jms_
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3. elevator pitch
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4. teaser examples
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5. (take 25 (squares-of (integers)))
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6. [‘1’,’2’,’3’,’4’].map(&:to_i).reduce(&:+)
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7. [1,2,3,4,5].filter(function(i) {
return i % 2 == 0;
});
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8. history
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9. lambda calculus
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10. declarative programming
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11. > how
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12. nested paradigms
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13. regex
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14. reactive programming
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15. domain specific languages
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16. functional programming
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17. languages
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18. concepts
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19. function() { }
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20. closures
function counter() {
var x = 0;
function increment(y) {
x += y;
console.log(x);
}
return increment;
}
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21. closures
first_counter = counter();
second_counter = counter();
first_counter(1)
first_counter(2)
first_counter(3)
second_counter(5)
second_counter(5)
second_counter(5)
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// returns 1
// returns 3
// returns 6
// returns 5
// returns 10
// returns 15

22. no side effects
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23. insanity
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24. ONE = 1;
add = lambda { |x, y|
x + y
}
addOne = lambda { |x|
add[x, ONE]
}
referential transparency
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25. require 'date'
opaque_millis = lambda {
DateTime.now.strftime('%Q').to_i
}
transparent_millis = lambda { |datetime|
datetime.strftime('%Q').to_i
}
referential transparency
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26. memoisation
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27. deforestation
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28. state is inevitable
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29. recursion
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30. structure and interpretation of computer programs
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31. examples
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32. list comprehension
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33. source = [1,2,3,4,5]
destination = []
for i in 0..source.length-1 do
destination << source[i]*2
end
return destination
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34. [1,2,3,4,5].map { |i| i * 2 }
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35. numbers = [1,2,3,4,5]
x = 0
for i in 1..numbers.length-1 do
x += numbers[i]
end
return x
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36. [1,2,3,4,5].reduce { |acc, x| acc + x }
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37. [1,2,3,4,5].reduce(&:+)
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38. mobile app frameworks
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39. Monday, 28 October 13

40. programming with nothing
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41. reactive extensions
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42. github desktop clients
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43. go forth and prosper!
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44. thanks
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