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comparison: samples/array_mapreduce.js
samples/array_mapreduce.js
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| 1 /* | |
| 2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. | |
| 3 * | |
| 4 * Redistribution and use in source and binary forms, with or without | |
| 5 * modification, are permitted provided that the following conditions | |
| 6 * are met: | |
| 7 * | |
| 8 * - Redistributions of source code must retain the above copyright | |
| 9 * notice, this list of conditions and the following disclaimer. | |
| 10 * | |
| 11 * - Redistributions in binary form must reproduce the above copyright | |
| 12 * notice, this list of conditions and the following disclaimer in the | |
| 13 * documentation and/or other materials provided with the distribution. | |
| 14 * | |
| 15 * - Neither the name of Oracle nor the names of its | |
| 16 * contributors may be used to endorse or promote products derived | |
| 17 * from this software without specific prior written permission. | |
| 18 * | |
| 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS | |
| 20 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, | |
| 21 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR | |
| 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR | |
| 23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, | |
| 24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | |
| 25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR | |
| 26 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
| 27 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING | |
| 28 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | |
| 29 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 30 */ | |
| 31 | |
| 32 // Usage: jjs array_mapreduce.js | |
| 33 | |
| 34 // Many Array.prototype functions such as map, | |
| 35 // filter, reduce, reduceRight, every, some are generic. | |
| 36 // These functions accept ECMAScript array as well as | |
| 37 // many array-like objects including java arrays. | |
| 38 // So, you can do map/filter/reduce with Java streams or | |
| 39 // you can also use Array.prototype functions as below. | |
| 40 // See also http://en.wikipedia.org/wiki/MapReduce | |
| 41 | |
| 42 var DoubleArray = Java.type("double[]"); | |
| 43 var StringArray = Java.type("java.lang.String[]"); | |
| 44 | |
| 45 var map = Array.prototype.map; | |
| 46 var filter = Array.prototype.filter; | |
| 47 var reduce = Array.prototype.reduce; | |
| 48 | |
| 49 var jarr = new StringArray(5); | |
| 50 jarr[0] = "nashorn"; | |
| 51 jarr[1] = "ecmascript"; | |
| 52 jarr[2] = "javascript"; | |
| 53 jarr[3] = "js"; | |
| 54 jarr[4] = "scheme"; | |
| 55 | |
| 56 // sum of word lengths | |
| 57 print("Sum word length:", | |
| 58 reduce.call( | |
| 59 map.call(jarr, function(x) x.length), | |
| 60 function(x, y) x + y) | |
| 61 ); | |
| 62 | |
| 63 // another array example involving numbers | |
| 64 jarr = new DoubleArray(10); | |
| 65 // make random array of numbers | |
| 66 for (var i = 0; i < jarr.length; i++) | |
| 67 jarr[i] = Math.random(); | |
| 68 | |
| 69 var forEach = Array.prototype.forEach; | |
| 70 // print numbers in the array | |
| 71 forEach.call(jarr, function(x) print(x)); | |
| 72 | |
| 73 // print sum of squares of the random numbers | |
| 74 print("Square sum:", | |
| 75 reduce.call( | |
| 76 map.call(jarr, function(x) x*x), | |
| 77 function(x, y) x + y) | |
| 78 ); |
