The slides created for the NationJS 2013 conference.

1. The Shape
of
Functional
Programming
Saturday, October 5, 13

2. @fogus
http://www.fogus.me
http://github.com/documentcloud/underscore-contrib
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3. @fogus
“Functional
JavaScript”Lemonad
codd.js
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4. A
program
written in an
object-oriented
style
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5. Functional
programming
for the MEOW!
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6. Saturday, October 5, 13

7. Pattern 1 - Map(ish)
var array = [0,1,2,3,4,5];
var transformed = [];
for (var i = 0; i < array.length; i++) {
transformed.push(array[i] + 100);
}
transformed;
//=> [100, 101, 102, 103, 104, 105]
Saturday, October 5, 13

8. Pattern 1 - Map(ish)
// Underscore
_.map(array, function(n) {
return n + 100;
});
// Lemonad
L.map(L.add(100), array);
Saturday, October 5, 13

9. Pattern 2 - Filter(ish)
var array = [0,1,2,3,4,5];
var keepers = [];
for (var i = 0; i < array.length; i++) {
if (array[i] % 2 === 0) {
keepers.push(array[i]);
}
}
keepers;
//=> [101, 102, 103, 104, 105]
Saturday, October 5, 13

10. Pattern 2 - Filter(ish)
// Underscore
_.filter(array, function(n) {
if (n % 2 === 0) {
return true;
}
else {
return false;
}
});
// Lemonad
L.filter(L.isEven, array);
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11. Pattern 3 - Reduce(ish)
var array = [0,1,2,3,4,5];
var sum = 0;
for (var i = 0; i < array.length; i++) {
sum += array[i];
}
sum;
//=> 15
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12. Pattern 3 - Reduce(ish)
// Underscore
_.reduce(array, function(acc, n) {
return acc + n;
}, 0);
// Lemonad
L.reduce(L.uncurry(L.add), 0, array);
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13. APL
life←{↑1 ⍵∨.∧3 4=+/,¯1 0 1∘.⊖¯1 0 1∘.⌽⊂⍵}
0 1 0 0 1 0 0 1 0
0 1 0
0 1 0
0 1 0
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14. Fun.js at a glance
• Simple data
• Many small functions
• Larger abstractions built via composition
• OO to supplement (no dogma)
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15. Simple data
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16. “
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17. #
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18. 42
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19. ?
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20. Saturday, October 5, 13

21. [ ]
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22. #
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23. #
[1, 2, 3, 4, 5]
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24. Saturday, October 5, 13

25. { }
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26. #“
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27. #“
{x: 0, y: 1}
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28. {x: 0, y: 1}
#
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29. Saturday, October 5, 13

30. *
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31. Small functions
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32. Saturday, October 5, 13

33. λ
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34. λ
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35. λ
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36. Disclaimer
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37. #
Procedure
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38. #
Procedure
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39. function logNth(array, index) {
console.log(array[index]);
}
logNth([‘a’, ‘b’, ‘c’], 1);
// (console) b
#
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40. Purity
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41. Ostrich Purity
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42. Ostrich Purity
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43. #
Function
Kinda important
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44. function nth(array, index) {
return array[index];
}
nth([‘a’, ‘b’, ‘c’], 1);
//=> ‘b’
#
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45. Saturday, October 5, 13

46. Saturday, October 5, 13

47. Saturday, October 5, 13

48. id name age
555-55-5555 Moe 45
777-77-7777 Curly 47
0
1
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49. var table = [
{id: ‘555-55-5555’,
name: ‘Moe’,
age: 45},
{id: ‘777-77-7777’,
name: ‘Curly’,
age: 47}
];
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50. id name age
555-55-5555 Moe 45
777-77-7777 Curly 47
0
1
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51. #“
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52. function cell(table, col, row){
return table[row][col];
}
cell(table, ‘name’, 0);
//=> ‘Moe’
cell(table, ‘age’, 0);
//=> 45
#“
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53. Larger abstractions
built via composition
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54. L
Clojure, Haskell, ML, Joy, _
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55. Currying, partial
application, fixation, oh
my!
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56. #“
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57. #“
L.fix
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58. #
L.fix(cell, L._, ‘name’, L._);
‘name’
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59. #
L.fix(cell, L._, ‘name’, L._);
var getName = L.fix(cell, L._, ‘name’, L._);
getName(table, 0);
//=> ‘Moe’
getName(table, 1);
//=> ‘Curly’
‘name’
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60. #“
L.rot
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61. #
L.rot(cell);
“
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62. #“
L.partial
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63. L.partial(L.rot(cell), ‘name’);
#‘name’
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64. L.partial(L.rot(cell), ‘name’);
var getName = L.partial(L.rot(cell), ‘name’);
getName(0, table);
//=> ‘Moe’
getName(1, table);
//=> ‘Curly’
#‘name’
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65. L.rcurry
“
Codd.col(table, ‘name’);
//=> [‘Moe’, ‘Curly’]
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66. “
“
L.rcurry2(Codd.col);
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67. “
L.rcurry2(Codd.col);
var valuesFor = L.rcurry2(Codd.col);
var allNames = valuesFor(‘name’);
allNames(table);
//=> [‘Moe’, ‘Curly’]
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68. Compositions and
Pipelines
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69. How to count
all of the values
in a column?
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70. “
function countValues(table, tag) {
return L.len(Codd.col(table, tag));
}
countValues(table, ‘name’);
//=> 2
#
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71. L.comp
return L.len(Codd.col(table, tag));
First thisThen this
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72. “Codd.col
#
L.len
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73. “Codd.col
#
L.len
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74. “
var countValues = L.comp(L.len, Codd.col);
countValues(table, ‘name’);
//=> 2
#
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75. L.pipeline
L.pipeline(table, Codd.col(‘name’), L.len);
//=> 2
First this Then this
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76. codd.js (demo)
Relational Algebra
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77. Thanks
• The NationJS team
• O’Reilly
• Alan Dipert
• Paul Khuong
• The Underscore community
• The Clojure community
Saturday, October 5, 13