static void Main(string[] args)
{
Func <int, int> square = x => x * x;
Console.WriteLine(square(5));
//Expression tree
System.Linq.Expressions.Expression <Func <int, int> > e = x => x * x;
Console.WriteLine(e);
int[] numbers = { 2, 3, 4, 5 };
var squaredNumbers = numbers.Select(x => x * x);
Console.WriteLine(string.Join(" ", squaredNumbers));
//Expression lambdas
Func <int, int, bool> testForEquality = (x, y) => x == y;
Console.WriteLine(testForEquality(5, 6));
//Statement lambdas
Action <string> greet = name =>
{
string greeting = $"Hello {name}!";
Console.WriteLine(greeting);
};
greet("World");
//Type inference in lambda expressions
var game = new VariableCaptureGame();
int gameInput = 5;
game.Run(gameInput);
int jTry = 10;
bool result = game.isEqualToCapturedLocalVariable(jTry);
Console.WriteLine($"Captured local variable is equal to {jTry}: {result}");
int anotherJ = 3;
game.updateCapturedLocalVariable(anotherJ);
bool equalToAnother = game.isEqualToCapturedLocalVariable(anotherJ);
Console.WriteLine($"Another lambda observes a new value of captured variable: {equalToAnother}");
}
static void Main(string[] args)
{
//IMPORTANT
//http://tutorials.jenkov.com/java/lambda-expressions.html
//A lambda expression is thus a function which can be created without belonging to any class.
//A lambda expression can be passed around as if it was an object and executed on demand.
//Lambda expressions are commonly used to implement simple event listeners / callbacks,
//or in functional programming with the Java Streams API.
//A lambda expression, in the world of computer programming, is a function not bound to
//an identifier.That also means it can be used as a variable or passed in as a method parameter.
//https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/statements-expressions-operators/lambda-expressions
//Lambda expressions can be written with a single or multiple lines.
//They can be assigned to variables or inline. LINQ, one of my favorite C# features,
//uses lambda expression. I’ll provide some sample code in C#.
//Any lambda expression can be converted to a delegate type.
//The delegate type to which a lambda expression can be converted is defined by the types of its
//parameters and return value.
//If a lambda expression doesn't return a value, it can be converted to one of the Action delegate types;
//otherwise, it can be converted to one of the Func delegate types.
//For example, a lambda expression that has two parameters and returns no value can be
//converted to an Action<T1,T2> delegate.
Action <int, int> sum = (num1, num2) => Console.WriteLine(num1 + num2);
sum(2, 4);
//A lambda expression that has one parameter and returns a value can be converted to a
//Func<T,TResult> delegate. In the following example, the lambda expression x => x * x,
//which specifies a parameter that's named x and returns the value of x squared,
//is assigned to a variable of a delegate type:
Func <int, int> square = x => x * x;
Console.WriteLine(square(5));
// Output:
// 25
Func <int, int, int> multiply = (x, y) => x * y;
Console.WriteLine(multiply(5, 2));
// Output:
// 25
//*Expression lambda that has an expression as its body:
//(input - parameters) => expression
//*Statement lambda that has a statement block as its body:
//(input - parameters) => { < sequence - of - statements > }
Action <string> greet = name =>
{
string greeting = $"Hello {name}!";
Console.WriteLine(greeting);
};
greet("World");
// Output:
// Hello World!
//Predicate
Predicate <int> equalsFive = x => x == 5;
bool result = equalsFive(4);
Console.WriteLine(result); // False
//Async Lambda Expressions
//button1.Click += async (sender, e) =>
//{
// await ExampleMethodAsync();
// textBox1.Text += "\r\nControl returned to Click event handler.\n";
//};
//===================================================================================
//Lambdas can refer to outer variables.These are the variables that are in scope
//in the method that defines the lambda expression, or in scope in the type that
//contains the lambda expression.
var game = new VariableCaptureGame();
int gameInput = 5;
game.Run(gameInput);
int jTry = 10;
bool resultX = game.isEqualToCapturedLocalVariable(jTry);
Console.WriteLine($"Captured local variable is equal to {jTry}: {resultX}");
int anotherJ = 3;
game.updateCapturedLocalVariable(anotherJ);
bool equalToAnother = game.isEqualToCapturedLocalVariable(anotherJ);
Console.WriteLine($"Another lambda observes a new value of captured variable: {equalToAnother}");
// Output:
// Local variable before lambda invocation: 0
// 10 is greater than 5: True
// Local variable after lambda invocation: 10
// Captured local variable is equal to 10: True
// 3 is greater than 5: False
// Another lambda observes a new value of captured variable: True
}
