C++ lambda表达式 （二）

#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 = 22;
   j = 44;
 
   // Call f and print its result.
   cout << f() << endl;
}

　　

可以看到i是拷贝值，j是引用值，所以是24，结果26

• 把lambda表达式当作参数传送

#include <list>
#include <algorithm>
#include <iostream>
int main()
{
    using namespace std;
    // Create a list of integers with a few initial elements.
    list<int> numbers;
    numbers.push_back();
    numbers.push_back();
    numbers.push_back();
    numbers.push_back();
    numbers.push_back();
 
    // Use the find_if function and a lambda expression to find the
    // first even number in the list.
    const list<int>::const_iterator result =
        find_if(numbers.begin(), numbers.end(),[](int n) { return (n % ) == ; });//查找第一个偶数
 
    // Print the result.
    if (result != numbers.end())
     {
        cout << "The first even number in the list is " << *result << "." << endl;
    } else
    {
        cout << "The list contains no even numbers." << endl;
    }
}

• lambda表达式嵌套使用

#include <iostream>
 
int main()
{
    using namespace std;
 
    // The following lambda expression contains a nested lambda
    // expression.
    int timestwoplusthree = [](int x) { return [](int y) { return y * ; }(x) + ; }();
 
    // Print the result.
    cout << timestwoplusthree << endl;
}

• ambda表达式使用在高阶函数里

#include <iostream>
#include <functional>
 
int main()
{
    using namespace std;
 
    auto addtwointegers = [](int x) -> function<int(int)> {
        return [=](int y) { return x + y; };
    };
 
    auto higherorder = [](const function<int(int)>& f, int z) {
        return f(z) * ;
    };
 
    // Call the lambda expression that is bound to higherorder.
    auto answer = higherorder(addtwointegers(), );
 
    // Print the result, which is (7+8)*2.
    cout << answer << endl;
}