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:DUQLQJ Ŏ /RWVRIFRGHVQLSSHWV Ŏ /RWVRIPDWKHTXDWLRQ

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Ŏ &RPSRVDEOHFROOHFWLRQGDWDRSHUDWLRQV

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)XQFWLRQ&RPSRVLWLRQ

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function incOne(input) { return input + 1; } function multTwo(input) { return input * 2; }

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function incOneMultTwo(input) { return (input + 1) * 2; }

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function incOneMultTwo(input) { return multTwo(incOne(input)); }

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z = f(y) y = g ( x ) z = f ( g ( x ))

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x g ! y f ! z

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z = h ( x ) h = f g

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h = f g ¯ h = g f

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f : X 7! X g : X 7! X

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whatever 7! whatever

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function multTwoIncOne(input) { return incOne(multTwo(input)); }

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var incOneMultTwo = compose(incOne, multTwo);

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function compose(f, g) { return function (input) { return f(g(input)); }; }

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0DS Ŏ $SSO\WUDQVIRUPDWLRQWRDOOHOHPHQWVRIJLYHQ FROOHFWLRQ

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map ( transform, coll ) ! coll 0

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[1,2,3,4].map(function (input) { return input + 1; }); // => [2,3,4,5]

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[1,2,3,4].map(incOne);
 // => [2,3,4,5]

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[1,2,3,4].map(incOneMultTwo);
 // => [4,6,8,10]

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reduce ( reducing, coll ) ! whatever

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[1,2,3,4].reduce(function(result, value) { return result + value; }, 0); // 10

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[1,2,3,4].reduce(function(result, value) { return result * value; }, 1); // 24

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[1,2,3,4].reduce(function(result, value) { return result.push(value); }, []); // [1, 2, 3, 4]

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whatever, input 7! whatever

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[1, 2, 3, 4].reduce(function(result, value) { return result + value; }, 0); // 10 whatever whatever input

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filter ( predicate, coll ) ! coll 0

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[1,2,3,4].filter(function (input) { return (input % 2 == 0); }); // [2, 4]

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function even (input) { return (input % 2 == 0); } [1,2,3,4].filter(even); // [2, 4]

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[1,2,3,4].map(function (input) { return input + 1; }); // => [2,3,4,5]

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[1,2,3,4].reduce(function (result, input) { return result.push(input + 1); }, []); // [2,3,4,5]

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[1,2,3,4].filter(function (input) { return (input % 2 == 0); }, []); // [2,4]

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[1,2,3,4].reduce(function (result, input) { return ( input % 2 == 0 ? concat(result, input) : result ); }, []) // => [2, 4]

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http://clojure.org/transducers (whatever, input 7! whatever) 7! (whatever, input 7! whatever)

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Ŏ ,QSXWUHGXFLQJIXQFWLRQ Ŏ 2XWSXWUHGXFLQJIXQFWLRQ Ŏ &RPSRVDEOH

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T : transducer R : reducing function Rmap Tfilter ! Rmap,filter

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map reducing function map transducer filter reducing function filter transducer take reducing function take transducer replace reducing function replace transducer

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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]; }) ) );

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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]; }) ) );

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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]; }) ) );

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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]; }) ) );

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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

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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

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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

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x g ! y f ! z

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x g ! y f ! z transducer reducing function

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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

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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

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x h ! z h = f g

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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

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x g ! y f ! z

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x g ! y f ! z coll 0 = reduce ( z, coll )

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x g ! y f ! z x g ! y f ! z

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Ŏ xLVODVWUHGXFLQJIXQFWLRQEXLOGWKHQHZFROOHFWLRQ IURPHOHPHQWV

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function (result, value) { return result.push(value); }

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function (result, value) { return result.append(value); }

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function (result, value) { return result[value[0]] = value[1]; }

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function (result, value) { return result.put(value); }

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 DQGLQLWLDOYDOXH perform reduce , CollReduce x

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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]

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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 )

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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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+RZ

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0DS coll.map(transform);

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0DSE\5HGXFH coll.reduce(function (result, input) { return concat(result, input + 1); }, []) CollReduce map transform

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function (result, input) { return concat(result, input + 1); }

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,QF2QH7UDQVGXFHU function (reducing) { return function (result, input) { return reducing(result, input + 1); }; } map transform CollReduce

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0DS7UDQVGXFHU&RQVWUXFWRU function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; }

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function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; } transducer constructor

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function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; } transducer x g ! y f ! z g

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function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; } reducing function

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function mapping(transform) { return function (reducing) { return function (result, input) { return reducing(result, transform(input)); }; }; } whatever

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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

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)LOWHU7UDQVGXFHU&RQVWUXFWRU function filtering(predicate) { return function (reducing) { return function (result, input) { return ( predicate(input) ? reducing(result, input) : result ); }; }; }

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7DNH7UDQVGXFHU&RQVWUXFWRU function taking(n) { return function (reducing) { return function (result, input) { if (n > 0) { n--; return reducing(result, input); } else { return result; } }; }; }

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'URS7UDQVGXFHU&RQVWUXFWRU function dropping(n) { return function (reducing) { return function (result, input) { if (n > 0) { n--; return result; } else { return reducing(result, input); } }; }; }

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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]; }) ) );

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https://github.com/jlongster/transducers.js

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Ŏ ,PSOHPHQWLWVRZQ&ROO5HGXFHSURWRFRO Ŏ ,PSOHPHQWUHGXFHEDVHGRQ&ORMXUHŇVGHVLJQ Ŏ :RUNZLWKMVFVS

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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]

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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

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&ORMXUH7UDQVGXFHU&RQVWUXFWRU (fn [xf] (fn ([] ...) ([result] ...) ([result input] ...)))

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[] Init: return initial value [result] Completion: some reduce operation require this step [result, input] Step: reducing function to build collection

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http://jlongster.com/Transducers.js--A-JavaScript-Library-for-Transformation-of-Data

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http://phuu.net/2014/08/31/csp-and-transducers.html

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