// even_lambda.cpp
// compile with: cl /EHsc /nologo /W4 /MTd
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main() 
{
 // Create a vector object that contains 10 elements.
 vector<int> v;
 for (int i = 1; i < 10; ++i) {
  v.push_back(i);
 }

 // Count the number of even numbers in the vector by 
 // using the for_each function and a lambda.
 int evenCount = 0;
 for_each(v.begin(), v.end(), [&evenCount] (int n) {
  cout << n;
  if (n % 2 == 0) {
   cout << "is even" << endl;
   ++evenCount;
  } else {
   cout << "is odd" << endl;
  }
 });

 // Print the count of even numbers to the console.
 cout << "There are " << evenCount 
  << " even numbers in the vector." << endl;
}

1 is even

2 is odd

3 is even

4 is odd

5 is even

6 is odd

7 is even

8 is odd

9 is even

There are 4 even numbers in the vector.

// even_functor.cpp
// compile with: /EHsc
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

class FunctorClass
{
public:
 // The required constructor for this example.
 explicit FunctorClass(int& evenCount)
  : m_evenCount(evenCount) { }

 // The function-call operator prints whether the number is
 // even or odd. If the number is even, this method updates
 // the counter.
 void operator()(int n) const {
  cout << n;

  if (n % 2 == 0) {
   cout << " is even " << endl;
   ++m_evenCount;
  } else {
   cout << " is odd " << endl;
  }
 }

private:
 // Default assignment operator to silence warning C4512.
 FunctorClass& operator=(const FunctorClass&);

 int& m_evenCount; // the number of even variables in the vector.
};


int main()
{
 // Create a vector object that contains 10 elements.
 vector<int> v;
 for (int i = 1; i < 10; ++i) {
  v.push_back(i);
 }

 // Count the number of even numbers in the vector by 
 // using the for_each function and a function object.
 int evenCount = 0;
 for_each(v.begin(), v.end(), FunctorClass(evenCount));

 // Print the count of even numbers to the console.
 cout << "There are " << evenCount
  << " even numbers in the vector." << endl;
}

1 is even

2 is odd

3 is even

4 is odd

5 is even

6 is odd

7 is even

8 is odd

9 is even

There are 4 even numbers in the vector.

// 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 an 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;
}

5
7

// 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 = 22;
 j = 44;

 // Call f and print its result.
 cout << f() << endl;
}

47

// 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;
}

// calling_lambda_expressions2.cpp
// compile with: /EHsc /W4
#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(13);
 numbers.push_back(17);
 numbers.push_back(42);
 numbers.push_back(46);
 numbers.push_back(99);

 // 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 % 2) == 0; });

 // 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;
 }
}

The first even number in the list is 42.

// nesting_lambda_expressions.cpp
// compile with: /EHsc /W4
#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 * 2; }(x) + 3; }(5);

 // Print the result.
 cout << timestwoplusthree << endl;
}

// higher_order_lambda_expression.cpp
// compile with: /EHsc /W4
#include <iostream>
#include <functional>

int main()
{
 using namespace std;

 // The following code declares a lambda expression that returns 
 // another lambda expression that adds two numbers. 
 // The returned lambda expression captures parameter x by value.
 auto addtwointegers = [](int x) -> function<int(int)> { 
  return [=](int y) { return x + y; }; 
 };

 // The following code declares a lambda expression that takes another
 // lambda expression as its argument.
 // The lambda expression applies the argument z to the function f
 // and multiplies by 2.
 auto higherorder = [](const function<int(int)>& f, int z) { 
  return f(z) * 2; 
 };

 // Call the lambda expression that is bound to higherorder. 
 auto answer = higherorder(addtwointegers(7), 8);

 // Print the result, which is (7+8)*2.
 cout << answer << endl;
}

void ApplyScale(const vector<int>& v) const
{
 for_each(v.begin(), v.end(), 
  [this](int n) { cout << n * _scale << endl; });
}

void ApplyScale(const vector<int>& v) const
{
 for_each(v.begin(), v.end(), 
  [=](int n) { cout << n * _scale << endl; });
}

// function_lambda_expression.cpp
// compile with: /EHsc /W4
#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

class Scale
{
public:
 // The constructor.
 explicit Scale(int scale) : _scale(scale) {}

 // Prints the product of each element in a vector object 
 // and the scale value to the console.
 void ApplyScale(const vector<int>& v) const
 {
  for_each(v.begin(), v.end(), [=](int n) { cout << n * _scale << endl; });
 }

private:
 int _scale;
};

int main()
{
 vector<int> values;
 values.push_back(1);
 values.push_back(2);
 values.push_back(3);
 values.push_back(4);

 // Create a Scale object that scales elements by 3 and apply
 // it to the vector object. Does not modify the vector.
 Scale s(3);
 s.ApplyScale(values);
}

3
6
9
12

// template_lambda_expression.cpp
// compile with: /EHsc
#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;

// Negates each element in the vector object. Assumes signed data type.
template <typename T>
void negate_all(vector<T>& v)
{
 for_each(v.begin(), v.end(), [](T& n) { n = -n; });
}

// Prints to the console each element in the vector object.
template <typename T>
void print_all(const vector<T>& v)
{
 for_each(v.begin(), v.end(), [](const T& n) { cout << n << endl; });
}

int main()
{
 // Create a vector of signed integers with a few elements.
 vector<int> v;
 v.push_back(34);
 v.push_back(-43);
 v.push_back(56);

 print_all(v);
 negate_all(v);
 cout << "After negate_all():" << endl;
 print_all(v);
}

34
-43
56
After negate_all():
-34
43
-56

// eh_lambda_expression.cpp
// compile with: /EHsc /W4
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;

int main()
{
 // Create a vector that contains 3 elements.
 vector<int> elements(3);

 // Create another vector that contains index values.
 vector<int> indices(3);
 indices[0] = 0;
 indices[1] = -1; // This is not a valid subscript. It will trigger an exception.
 indices[2] = 2;

 // Use the values from the vector of index values to 
 // fill the elements vector. This example uses a 
 // try/catch block to handle invalid access to the 
 // elements vector.
 try
 {
  for_each(indices.begin(), indices.end(), [&](int index) { 
   elements.at(index) = index; 
  });
 }
 catch (const out_of_range& e)
 {
  cerr << "Caught '" << e.what() << "'." << endl;
 };
}

Caught 'invalid vector<T> subscript'.

// managed_lambda_expression.cpp
// compile with: /clr
using namespace System;

int main()
{
 char ch = '!'; // a local unmanaged variable

 // The following lambda expression captures local variables
 // by value and takes a managed String object as its parameter.
 [=](String ^s) { 
  Console::WriteLine(s + Convert::ToChar(ch)); 
 }("Hello");
}

Hello!