What are lambda expressions in C++?

Question

Accepted Answer

**Lambda** — anonymous function object.

**Basic syntax:**
```cpp
auto add = [](int a, int b) -> int {
    return a + b;
};

int result = add(3, 4); // 7
```

**Capture modes:**
```cpp
int x = 10;
auto f1 = [x]() { return x; };      // copy x
auto f2 = [&x]() { x += 1; };       // reference x
auto f3 = [=]() { return x; };       // copy all by value
auto f4 = [&]() { x += 1; };        // reference all
auto f5 = [x = x + 1]() { return x; }; // init capture
```

**Mutable lambdas:**
```cpp
auto counter = [count = 0]() mutable {
    return ++count;
};
```

**Generic lambdas (C++14):**
```cpp
auto add = [](auto a, auto b) { return a + b; };
```

C++: What are lambda expressions in C++?