I just can't seem to ponder Lambdas in C #

Question

I really could not get a clear idea about creating and using lambda expressions. I know how to use them in linq expressions, but I really don't understand what is going on behind the scenes. I also could not find a complete tutorial on when to use them, how to identify them, etc.

The second part of...

They say that Javascript is the LAMBDA language, I know javascript pretty well, I just wonder what types of concepts apply to javascript lambdas and C # lambdas.

thrid part ...

What is the difference between a functional language and a lambda language?

Any suggestions?

Answer 1

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delegate int D(int x);
...
class C
{
    void M(int y)
    {
        int z = 123;
        D d = x=>x+y+z;
        Console.WriteLine(d(10));
        z = 345;
        y = 789;
        Console.WriteLine(d(10));
   }
}

, :

delegate int D(int x);
...
class C
{  
    private class Locals
    {
        public int y;
        public int z;
        public int A(int x)
        {
            return x + this.y + this.z;
        }
    }
    void M(int y)
    {
        // Initialize the closure class:

        Locals locals = new Locals();
        locals.y = y;

        // Transform the body so that all usages of y, z and the lambda
        // refer to the closure class:

        locals.z = 123;
        D d = locals.A;
        Console.WriteLine(d(10)); // Calls locals.A(10)
        locals.z = 345;
        locals.y = 789;
        Console.WriteLine(d(10)); // Calls locals.A(10)

    }
}

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Answer 2

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Answer 3

JavaScript. JS (var fn = function(){/* stuff */};), . , lambdas, - . :

// Standard sort:
x = [4,3,6,7,1,5,2];
x.sort();

// Custom sort:
y = [
    {'val':4,'name':'four'},
    {'val':3,'name':'three'},
    {'val':6,'name':'six'},
    {'val':7,'name':'seven'},
    {'val':1,'name':'one'},
    {'val':5,'name':'five'},
    {'val':2,'name':'two'},
];
y.sort(function(a,b){ return a.val > b.val ? 1 : -1 });

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, Widget. , Widget.prototype.publish() , :

var Widget = function() {
    var self = this;
    var strPrivateVar = "This is a private variable";
    self.publicVar = "This is a default public variable";
    self.publish = function(f) {
        var fnFormatter = f;
        var strOutput = "The output is " + fnFormatter(self,strPrivateVar);
        return strOutput;
    }
};

, formatters. , :

var fnSummary = function(o,s) {
    var self = o;
    var strPrivateVar = s;
    return strPrivateVar.substr(0,5) + ' ' + self.publicVar.substr(0,5);
}
var fnDetails = function(o,s) {
    var self = o; 
    var strPrivateVar = s;
    return strPrivateVar + ' ' + self.publicVar;
}

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var wWidget = new Widget();
wWidget.publicVar = "I have overridden the public property";
var strSummary = wWidget.publish(fnSummary);
var strDetails = wWidget.publish(fnDetails);
console.log(strSummary,strDetails);

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Answer 4

http://msdn.microsoft.com/en-us/magazine/cc163362.aspx .

Answer 5

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Answer 6

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Answer 7

Lambda - "" , #. http://msdn.microsoft.com/en-us/library/bb397687(VS.90).aspx

Lambada - " ", .

http://www.rvenables.com/tag/lambda-expressions/ , lambada.

http://www.codeproject.com/KB/cs/DelegatesOMy.aspx pre/post lambda.

Answer 8

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public void Run()
{
    var template = "{0} inches is {1} centimetres.";
    Console.WriteLine(template, 2.0, 2.0 * 2.54);
    Console.WriteLine(template, 5.0, 5.0 * 2.54);
}

, * 2.54, ​​:

private double Inches2Centimetres(double inches)
{
    return inches * 2.54;
}

:

public void Run()
{
    var template = "{0} inches is {1} centimetres.";
    Console.WriteLine(template, 2.0, Inches2Centimetres(2.0));
    Console.WriteLine(template, 5.0, Inches2Centimetres(5.0));
}

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public void Run()
{
    Func<double, double> inches2Centimetres = inches => inches * 2.54;

    var template = "{0} inches is {1} centimetres.";
    Console.WriteLine(template, 2.0, inches2Centimetres(2.0));
    Console.WriteLine(template, 5.0, inches2Centimetres(5.0));
}

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public static T[] UsingDataReader<T>(
    this IDbConnection @this,
    string query,
    Func<IDataReader, T> transform)
{
    //...
}

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string[] names = conn.UsingDataReader<string>("select FirstName from People;",
    dr => dr["FirstName"] as string);

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Answer 9

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