What are C++ lambda functions and how do they capture variables?

What are C++ lambda functions and how do they capture variables?

C++ lambda functions are anonymous functions that can capture variables from their surrounding scope. They allow for concise function definitions.

Can you give me an example of a lambda function capturing a variable?

Sure! Here's a simple example:

int x = 10;
auto lambda = [&x]() { return x + 5; };
std::cout << lambda(); // Outputs 15

In this case, the lambda captures the variable x by reference.

What happens if I capture by value instead?

If you capture by value, the lambda gets a copy of the variable. Changes to the original variable won't affect the captured value.

Can you show me an example of capturing by value?

Absolutely! Here's an example:

int x = 10;
auto lambda = [x]() { return x + 5; };
std::cout << lambda(); // Outputs 15
x = 20;
std::cout << lambda(); // Still outputs 15

Here, the lambda captures x by value, so it retains the original value.