njlr

int x = 2;
int y = 9;
int z = 4;

// f captures nothing
std::function<int(int)> f = [](int i) {
  return i + 1;
};

// g captures x, y and z

njlr

struct Functor {
  // The context, or capture
  // For example, an int and an unsigned
  int i;
  unsigned N;
  
  // The lambda
  int operator() (int j) const {
    // For example, a small math function
    return i * j + N;

njlr

struct SomeClassWithAReallyLongName {
  // ... 
};

SomeClassWithAReallyLongName foo() {
  SomeClassWithAReallyLongName x;
  return x;
}

int main() {

njlr

Vector<1> v;
Vector<2> v;
Vector<3> u;
// etc... 

njlr

template<int D>
struct Vector {
  
  static constexpr unsigned N = D;
  int data[N];
  
  Vector(int fill = 0) {
    for (int i = 0; i < N; ++i) {
      data[i] = fill;
    }

njlr

public final class Vector3 {
 
  public final float x;
  public final float y;
  public final float z;
 
  public Vector3(float x, float y, float z) {
    this.x = x;
    this.y = y;
    this.z = z;

njlr

Vector2 v = { 1, 2 };
Vector2 u = { 3, 4 };
Vector2 w = v + w; // Much better!

njlr

struct Vector2 {
  float x;
  float y;
};

inline Vector2 operator+(Vector2 const& lhs, Vector2 const& rhs) {
  return { lhs.x + rhs.x, lhs.y + lhs.y };
}

njlr

Vector2 v = new Vector2(1, 2);
Vector2 u = new Vector2(3, 4);
Vector2 w = v.add(w);

njlr

public final class Vector2 {
 
  public final float x;
  public final float y;
 
  public Vector2(float x, float y) {
    this.x = x;
    this.y = y;
  }