what is a lambda function in c++ code example

Example 1: lambda c++

#include <iostream>
#include <string>
 
// returns a lambda
auto makeWalrus(const std::string& name)
{
  // Capture name by reference and return the lambda.
  return [&]() {
    std::cout << "I am a walrus, my name is " << name << '\n'; // Undefined behavior
  };
}
 
int main()
{
  // Create a new walrus whose name is Roofus.
  // sayName is the lambda returned by makeWalrus.
  auto sayName{ makeWalrus("Roofus") };
 
  // Call the lambda function that makeWalrus returned.
  sayName();
 
  return 0;
}

Example 2: cpp lambda function

#include <iostream>
using namespace std;

bool isGreater = [](int a, int b){ return a > b; }

int main() {
	cout << isGreater(5, 2) << endl; // Output: 1
	return 0;
}

Example 3: cpp lambda

struct X {
    int x, y;
    int operator()(int);
    void f()
    {
        // the context of the following lambda is the member function X::f
        [=]()->int
        {
            return operator()(this->x + y); // X::operator()(this->x + (*this).y)
                                            // this has type X*
        };
    }
};