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// Usage: jjs array_mapreduce.js

// Many Array.prototype functions such as map, 

// filter, reduce, reduceRight, every, some are generic.

// These functions accept ECMAScript array as well as 

// many array-like objects including java arrays.

// So, you can do map/filter/reduce with Java streams or

// you can also use Array.prototype functions as below.

// See also http://en.wikipedia.org/wiki/MapReduce

var DoubleArray = Java.type("double[]");

var StringArray = Java.type("java.lang.String[]");

var map = Array.prototype.map;

var filter = Array.prototype.filter;

var reduce = Array.prototype.reduce;

var jarr = new StringArray(5);

jarr[0] = "nashorn";

jarr[1] = "ecmascript";

jarr[2] = "javascript";

jarr[3] = "js";

jarr[4] = "scheme";

// sum of word lengths

print("Sum word length:",

    reduce.call(

        map.call(jarr, function(x) x.length),

        function(x, y) x + y)

);

// another array example involving numbers

jarr = new DoubleArray(10);

// make random array of numbers

for (var i = 0; i < jarr.length; i++)

    jarr[i] = Math.random();

var forEach = Array.prototype.forEach;

// print numbers in the array

forEach.call(jarr, function(x) print(x));

// print sum of squares of the random numbers

print("Square sum:",

    reduce.call(

        map.call(jarr, function(x) x*x), 

        function(x, y) x + y)

);