An example of a LAMBDA expression

Turn from: https://msdn.microsoft.com/zh-cn/library/dd293599.aspx

This article demonstrates how to use a lambda expression in your program. For an overview of lambda expressions, see lambda expressions in C + +. For more information about the structure of lambda expressions, see lambda expression syntax. declaring a LAMBDA expression Example 1

Because the lambda expression is typed, you can assign it to the auto variable or function object as follows: code C + +

Declaring_lambda_expressions1.cpp
//compile with:/ehsc/w4
#include <functional>
#include < iostream>

int main ()
{

    using namespace std;

    Assign The lambda expression that adds two numbers to a auto variable.
    Auto F1 = [] (int x, int y) {return x + y;};

    cout << F1 (2, 3) << Endl;

    Assign the same lambda expression to a function object.
    Function<int (int, int) > F2 = [] (int x, int y) {return x + y;};

    cout << F2 (3, 4) << Endl;
}

Output

5
7

Note

For more information, see Automatic (c + +, function class, and function calls (C + +).

Although many lambda expressions are declared in the body of a function, they can be declared anywhere in the initialization variable. Example 2

The Visual C + + compiler binds the expression to the captured variable when it declares rather than invokes a lambda expression. The following example shows a lambda expression that captures the local variable I by value and captures the local variable J by reference. Because a lambda expression captures I through a value, reassigning I in the later part of the program does not affect the result of the expression. However, because a lambda expression captures J by reference, Reassigning J affects the result of the expression. Code C + +

Declaring_lambda_expressions2.cpp
//compile with:/ehsc/w4
#include <functional>
#include < iostream>

int main ()
{
   using namespace std;

   int i = 3;
   int j = 5;

   The following lambda expression captures I by value and
   //J by reference.
   Function<int (void) > f = [i, &j] {return i + j;};

   Change the values of I and J.
   i =;
   j =;

   Call F and print it result.
   cout << F () << Endl;
}

Output

47

Call LAMBDA expression

You can call the lambda expression immediately, as shown in the following code fragment. The second code fragment demonstrates how to pass a lambda as a parameter to the Standard Template Library (STL) algorithm, such as find_if. Example 1

The following example declares a lambda expression that returns the sum of two integers and calls the expression immediately using Parameters 5 and 4: code C + +

Calling_lambda_expressions1.cpp
//compile with:/EHsc
#include <iostream>

int main ()
{
   using namespace std;
   int n = [] (int x, int y) {return x + y;} (5, 4);
   cout << n << endl;
}

Output

9

Example 2

The following example passes a lambda expression as a parameter to the find_if function. Returns trueif the lambda expression has an even number of arguments. Code