lambda c 2b 2b

1- Good website to learn lambda in c++:
2https://docs.microsoft.com/en-us/cpp/cpp/lambda-expressions-in-cpp
3https://en.cppreference.com/w/cpp/language/lambda
4https://www.geeksforgeeks.org/lambda-expression-in-c/
5https://stackoverflow.com/questions/7627098/what-is-a-lambda-expression-in-c11
6https://linuxhint.com/lambda-expressions-in-c/

1#include <iostream>
2using namespace std;
3
4bool isGreater = [](int a, int b){ return a > b; }
5
6int main() {
7	cout << isGreater(5, 2) << endl; // Output: 1
8	return 0;
9}
10

1#include <iostream>
2#include <string>
3 
4// returns a lambda
5auto makeWalrus(const std::string& name)
6{
7  // Capture name by reference and return the lambda.
8  return [&]() {
9    std::cout << "I am a walrus, my name is " << name << '\n'; // Undefined behavior
10  };
11}
12 
13int main()
14{
15  // Create a new walrus whose name is Roofus.
16  // sayName is the lambda returned by makeWalrus.
17  auto sayName{ makeWalrus("Roofus") };
18 
19  // Call the lambda function that makeWalrus returned.
20  sayName();
21 
22  return 0;
23}
24

1struct X {
2    int x, y;
3    int operator()(int);
4    void f()
5    {
6        // the context of the following lambda is the member function X::f
7        [=]()->int
8        {
9            return operator()(this->x + y); // X::operator()(this->x + (*this).y)
10                                            // this has type X*
11        };
12    }
13};

1//lambda function for sorting vector ascending
2sort(vec.begin(),vec.end(),[](int &a, int &b){
3	return a<b;
4});
5//lambda function for sorting vector of vector ascending based on first value
6sort(vec.begin(),vec.end(),[](vector<int> &a, vector<int> &b){
7	return a[0]<b[0];
8});