---
title: "Lambda expressions in C++"
description: "C++ lambda expressions explained: syntax, capture lists, capturing by value, mutable lambdas, and using lambdas with standard algorithms."
date: 2023-04-06
last_modified_at: 2026-10-02
keywords: [C++, lambda expressions, C++11, closures, capture list]
---

# Lambda Expressions in C++

Lambda expressions were introduced in C++11 and provide a concise way to create anonymous function objects.

## Basic Syntax

The basic syntax of a lambda expression is:

```cpp
[capture-list](parameter-list) -> return-type { function-body }
```

Where:
- `capture-list`: Specifies which variables from the surrounding scope are accessible
- `parameter-list`: Similar to function parameters
- `return-type`: Optional, compiler can often deduce it
- `function-body`: The code to execute

## Examples

### Simple Lambda

```cpp
auto add = [](int a, int b) { return a + b; };
std::cout << add(5, 3); // Outputs: 8
```

### Capturing Variables

```cpp
int multiplier = 5;
auto multiply = [multiplier](int x) { return x * multiplier; };
std::cout << multiply(3); // Outputs: 15
```

### Mutable Lambda

By default, variables captured by value cannot be modified. Use the `mutable` keyword to allow modification:

```cpp
int counter = 0;
auto increment = [counter]() mutable { return ++counter; };
std::cout << increment(); // Outputs: 1
std::cout << counter;     // Outputs: 0 (original not modified)
```

Lambda expressions are commonly used with algorithms from the standard library, such as `std::sort`, `std::for_each`, and `std::transform`.