Transducer

Explain transducer in JS code snippets

Transcript

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6. function incOne(input) { return input + 1; } function multTwo(input) { return input * 2; }
7. function incOneMultTwo(input) { return (input + 1) * 2; }
8. function incOneMultTwo(input) { return multTwo(incOne(input)); }
9. z = f(y) y = g ( x ) z = f ( g ( x ))
10. x g ! y f ! z
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12. h = f g ¯ h = g f
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14. f : X 7! X g : X 7! X
15. whatever 7! whatever
16. function multTwoIncOne(input) { return incOne(multTwo(input)); }
17. var incOneMultTwo = compose(incOne, multTwo);
18. function compose(f, g) { return function (input) { return f(g(input)); }; }
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21. 0DS Ŏ $SSO\WUDQVIRUPDWLRQWRDOOHOHPHQWVRIJLYHQ FROOHFWLRQ
22. map ( transform, coll ) ! coll 0
23. [1,2,3,4].map(function (input) { return input + 1; }); // => [2,3,4,5]
24. [1,2,3,4].map(incOne);
 // => [2,3,4,5]
25. [1,2,3,4].map(incOneMultTwo);
 // => [4,6,8,10]
26. 5HGXFH Ŏ 5HGXFHDFROOHFWLRQWRDVLQJOHYDOXH
27. reduce ( reducing, coll ) ! whatever
28. [1,2,3,4].reduce(function(result, value) { return result + value; }, 0); // 10
29. [1,2,3,4].reduce(function(result, value) { return result * value; }, 1); // 24
30. [1,2,3,4].reduce(function(result, value) { return result.push(value); }, []); // [1, 2, 3, 4]
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32. whatever, input 7! whatever
33. [1, 2, 3, 4].reduce(function(result, value) { return result + value; }, 0); // 10 whatever whatever input
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36. )LOWHU Ŏ 5HWXUQQHZFROOHFWLRQZLWKZDQWHGHOHPHQW RQO\XVHSUHGLFDWHIXQFWLRQ
37. filter ( predicate, coll ) ! coll 0
38. [1,2,3,4].filter(function (input) { return (input % 2 == 0); }); // [2, 4]
39. function even (input) { return (input % 2 == 0); } [1,2,3,4].filter(even); // [2, 4]
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42. [1,2,3,4].map(function (input) { return input + 1; }); // => [2,3,4,5]
43. [1,2,3,4].reduce(function (result, input) { return result.push(input + 1); }, []); // [2,3,4,5]
44. [1,2,3,4].filter(function (input) { return (input % 2 == 0); }, []); // [2,4]
45. [1,2,3,4].reduce(function (result, input) { return ( input % 2 == 0 ? concat(result, input) : result ); }, []) // => [2, 4]
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51. http://clojure.org/transducers (whatever, input 7! whatever) 7! (whatever, input 7! whatever)
52. Ŏ ,QSXWUHGXFLQJIXQFWLRQ Ŏ 2XWSXWUHGXFLQJIXQFWLRQ Ŏ &RPSRVDEOH
53. T : transducer R : reducing function Rmap Tfilter ! Rmap,filter
54. map reducing function map transducer filter reducing function filter transducer take reducing function take transducer replace reducing function replace transducer
55. var c = chan( 1, // buffer size compose( // Only events with even x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) );
56. var c = chan( 1, // buffer size compose( // Only events with page x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) );
57. var c = chan( 1, // buffer size compose( // Only events with page x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) );
58. var c = chan( 1, // buffer size compose( // Only events with page x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) );
59. var c = chan( 1, // buffer size compose( // Only events with page x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) ); transducer transducer
60. var c = chan( 1, // buffer size compose( // Only events with page x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) ); filter transducer constructor map transducer constructor
61. var c = chan( 1, // buffer size compose( // Only events with page x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) ); filter predicate map transform
62. x g ! y f ! z
63. x g ! y f ! z transducer reducing function
64. var c = chan( 1, // buffer size compose( // Only events with page x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) ); f
65. var c = chan( 1, // buffer size compose( // Only events with even x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) ); g
66. x h ! z h = f g
67. var c = chan( 1, // buffer size // Only events with even x & y // And transform format to [type, x, y] compose( // Only events with even x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) ); h
68. x g ! y f ! z
69. x g ! y f ! z coll 0 = reduce ( z, coll )
70. x g ! y f ! z x g ! y f ! z
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73. function (result, value) { return result.push(value); }
74. function (result, value) { return result.append(value); }
75. function (result, value) { return result[value[0]] = value[1]; }
76. function (result, value) { return result.put(value); }
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 DQGLQLWLDOYDOXH perform reduce , CollReduce x
79. var receipt = compose( mapping(incOne), filtering(even) ); var reduceToArray = function (result, input) { return result.push(input); } [1,2,3,4].reduce( receipt(reduceToArray) , []); // [2, 4]
80. var receipt = compose( mapping(incOne), filtering(even) ); var reduceToArray = function (result, input) { return result.push(input); } [1,2,3,4].reduce( receipt(reduceToArray) , []); // [2, 4] x h z h ( x )
81. var receipt = compose( mapping(incOne), filtering(even) ); var reduceToArray = function (result, input) { return result.push(input); } [1, 2, 3, 4].reduce( receipt(reduceToArray) , []); // [2, 4] CollReduce initial value iterate
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83. 5HGXFLQJ)XQFWLRQ 7UDQVIRUP
84. +RZ
85. 0DS coll.map(transform);
86. 0DSE\5HGXFH coll.reduce(function (result, input) { return concat(result, input + 1); }, []) CollReduce map transform
87. %XLOGIURP&ROO5HGXFH 3URWRFRO
88. function (result, input) { return concat(result, input + 1); }
89. 'HFRXSOH&ROO5HGXFH
90. ,QF2QH7UDQVGXFHU function (reducing) { return function (result, input) { return reducing(result, input + 1); }; } map transform CollReduce
91. 'HFRXSOH7UDQVIRUP
92. 0DS7UDQVGXFHU&RQVWUXFWRU function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; }
93. function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; } transducer constructor
94. function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; } transducer x g ! y f ! z g
95. function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; } reducing function
96. function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; } whatever
97. function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; } CollReduce initial value map transform x y x g ! y f ! z x g ! y f ! z
98. )LOWHU7UDQVGXFHU&RQVWUXFWRU function filtering(predicate) { return function (reducing) { return function (result, input) { return ( predicate(input) ? reducing(result, input) : result ); }; }; }
99. 7DNH7UDQVGXFHU&RQVWUXFWRU function taking(n) { return function (reducing) { return function (result, input) { if (n > 0) { n--; return reducing(result, input); } else { return result; } }; }; }
100. 'URS7UDQVGXFHU&RQVWUXFWRU function dropping(n) { return function (reducing) { return function (result, input) { if (n > 0) { n--; return result; } else { return reducing(result, input); } }; }; }
101. var c = chan( 1, // buffer size compose( // Only events with even x & y filtering(function (e) { return ( even(e.pageX) && even(e.pageY) ); }), // e -> [type, x, y] mapping(function (e) { return [e.type, e.pageX, e.pageY]; }) ) );
102. 7UDQVGXFHUMV
103. https://github.com/jlongster/transducers.js
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105. var map = t.map, filter = t.filter, comp = t.comp, into = t.into, apush = function(arr, x) { arr.push(x); return arr; }, var inc = function(n) { return n + 1; }; var isEven = function(n) { return n % 2 == 0; }; var xf = comp(map(inc), filter(isEven)); into([], xf, [0,1,2,3,4]); // [2,4] transduce(xf, apush, 0, [0,1,2,3,4]); // [2,4]
106. var map = t.map, filter = t.filter, comp = t.comp, into = t.into, apush = function(arr, x) { arr.push(x); return var inc = function(n) { return n + 1; }; var isEven = function(n) { return n % 2 == 0; }; var xf = comp(map(inc), filter(isEven)); into([], xf, [0,1,2,3,4]); // [2,4] transduce(xf, apush, 0, [0,1,2,3,4]); // [2,4] CollReduce transducer initial value coll
107. &ORMXUH7UDQVGXFHU&RQVWUXFWRU (fn [xf] (fn ([] ...) ([result] ...) ([result input] ...)))
108. [] Init: return initial value [result] Completion: some reduce operation require this step [result, input] Step: reducing function to build collection
109. http://jlongster.com/Transducers.js--A-JavaScript-Library-for-Transformation-of-Data
110. http://phuu.net/2014/08/31/csp-and-transducers.html
111. Q?