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

What are lambda expressions in C++?

Lambda expressions in C++ are a way to create anonymous functions. They allow you to define a function inline without needing to create a separate function definition.

How do lambda expressions capture variables by value?

When a lambda captures variables by value, it makes a copy of the variable's value at the time the lambda is created. This means changes to the original variable won't affect the lambda's copy.

Can you give me an example of capturing by value?

Sure! 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 change the original variable after creating the lambda?

If you change the original variable after creating the lambda, the lambda will still use the value it captured at the time of its creation. For example:

x = 20;
std::cout << lambda(); // Still outputs 15