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

Can you explain what C++ lambda functions are?

Sure! C++ lambda functions are anonymous functions that can be defined in-line. They allow you to create function objects without needing to define a separate function.

How do they capture variables by value?

When a lambda captures by value, it makes a copy of the variable's value at the time the lambda is created. This means the lambda can use that value even if the original variable changes later.

Can you give me an example of capturing by value?

Absolutely! Here's a simple example:

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

In this case, x is captured by value, so the lambda uses the value 10.

What happens if I modify the original variable after creating the lambda?

If you modify the original variable after the lambda is created, the lambda will still use the original value it captured. For example, if you set x = 20; after creating the lambda, it will still return 15 when called.