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<title>linq.js tutorial</title>
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<h2>
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First step of Lambda Expression</h2>
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<pre>
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// Anonymous function
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Enumerable.Range(1, 3).Select(function(value, index) { return index + ':' + value }).WriteLine();
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// String like Lambda Expression (arguments => expression)
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Enumerable.Range(1, 3).Select("value,index=>index+':'+value").WriteLine();
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// If the number of arguments is one , can use default iterator variable '$'
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Enumerable.Range(1, 3).Select("i=>i*2").WriteLine();
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Enumerable.Range(1, 3).Select("$*2").WriteLine(); // same
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// "" is shortcut of "x => x" (identity function)
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Enumerable.Range(4, 7).Join(Enumerable.Range(8, 5), "", "", "outer,inner=>outer*inner").WriteLine();
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</pre>
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<h2>
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Scope of lambda expression</h2>
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<pre>
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var number = 3;
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// Can't Find number | lambda expression can use only global variable
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// Enumerable.Range(1,10).Where("$ == number").WriteLine();
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// use anonymous founction, can capture variable
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Enumerable.Range(1,10).Where(function(i){return i == number}).WriteLine();
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</pre>
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<h2>
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From(Object) -> convert to KeyValuePair</h2>
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<pre>
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var object = {foo:"a", "bar":100, "foobar":true};
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Enumerable.From(object).ForEach(function(obj)
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{
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document.write(obj.Key + ":" + obj.Value + "<br />");
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})
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</pre>
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<h2>
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ForEach (continue and break)</h2>
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<pre>
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Enumerable.Repeat("foo", 10).ForEach(function(value, index)
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{
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if (index % 2 == 0) return; // continue
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if (index > 6) return false; // break
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document.write(index + ":" + value + "<br />");
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});
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</pre>
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<h2>
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Grouping and ref/value compare</h2>
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<pre>
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// ref compare
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document.write((new Date(2000, 1, 1) == new Date(2000, 1, 1)) + "<br />"); // false
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document.write(({ a: 0} == { a: 0 }) + "<br />"); // false
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document.write("------" + "<br />");
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var objects = [
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{ Date: new Date(2000, 1, 1), Id: 1 },
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{ Date: new Date(2010, 5, 5), Id: 2 },
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{ Date: new Date(2000, 1, 1), Id: 3 }
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]
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// ref compare, can not grouping
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Enumerable.From(objects)
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.GroupBy("$.Date", "$.Id",
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function (key, group) { return { date: key, ids: group.ToString(',')} })
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.WriteLine("$.date + ':' + $.ids");
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document.write("------" + "<br />");
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// use fourth argument(compareSelector)
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Enumerable.From(objects)
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.GroupBy("$.Date", "$.Id",
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function (key, group) { return { date: key, ids: group.ToString(',')} },
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function (key) { return key.toString() })
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.WriteLine("$.date + ':' + $.ids");
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</pre>
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<h2>
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Regular Expression Matches</h2>
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<pre>
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// Enumerable.Matches return Enumerable<MatchObject>
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var input = "abcdefgABzDefabgdg";
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Enumerable.Matches(input, "ab(.)d", "i").ForEach(function(match)
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{
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for (var prop in match)
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{
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document.write(prop + " : " + match[prop] + "<br />");
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}
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document.write("toString() : " + match.toString() + "<br />");
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document.write("---" + "<br />");
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});
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</pre>
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<h2>
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LazyEvaluation and InfinityList</h2>
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<pre>
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// first radius of circle's area over 10000
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var result = Enumerable.ToInfinity(1).Where("r=>r*r*Math.PI>10000").First();
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document.write(result);
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</pre>
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<h2>
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Dictionary</h2>
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<pre>
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// sample class
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var cls = function (a, b)
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{
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this.a = a;
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this.b = b;
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}
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var instanceA = new cls("a", 100);
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var instanceB = new cls("b", 2000);
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// create blank dictionary
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var dict = Enumerable.Empty().ToDictionary();
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// create blank dictionary(use compareSelector)
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var dict = Enumerable.Empty().ToDictionary("","",function (x) { return x.a + x.b });
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dict.Add(instanceA, "zzz");
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dict.Add(instanceB, "huga");
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document.write(dict.Get(instanceA) + "<br />"); // zzz
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document.write(dict.Get(instanceB) + "<br />"); // huga
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// enumerable (to KeyValuePair)
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dict.ToEnumerable().ForEach(function (kvp)
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{
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document.write(kvp.Key.a + ":" + kvp.Value + "<br />");
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});
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</pre>
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<h2>
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sample - Nondeterministic Programs</h2>
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// from Structure and Interpretation of Computer Programs 4.3.2
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<pre>
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var apart = Enumerable.Range(1, 5);
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var answers = apart
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.SelectMany(function(baker){ return apart
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.SelectMany(function(cooper){ return apart
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.SelectMany(function(fletcher){ return apart
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.SelectMany(function(miller){ return apart
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.Select(function(smith){ return {
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baker: baker, cooper: cooper, fletcher: fletcher, miller: miller, smith: smith}})})})})})
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.Where("Enumerable.From($).Distinct('$.Value').Count() == 5")
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.Where("$.baker != 5")
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.Where("$.cooper != 1")
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.Where("$.fletcher != 1 && $.fletcher != 5")
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.Where("$.miller > $.cooper")
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.Where("Math.abs($.smith - $.fletcher) != 1")
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.Where("Math.abs($.fletcher - $.cooper) != 1");
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answers.SelectMany("").WriteLine("$.Key + ':' + $.Value");
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</pre>
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