What are some examples of capturing lambda expressions in C++?

What are some examples of capturing lambda expressions in C++?

Capturing lambda expressions in C++ allow you to use variables from the surrounding scope. Here are a few examples:

1. By Value: auto lambda = [x]() { return x + 1; }; captures x by value.
2. By Reference: auto lambda = [&x]() { x += 1; }; captures x by reference.
3. Mixed Capture: auto lambda = [x, &y]() { return x + y; }; captures x by value and y by reference.

Can you explain the difference between capturing by value and by reference?

Sure! Capturing by value means that the lambda makes a copy of the variable, so changes to the original variable won't affect the copy. Capturing by reference means the lambda uses the original variable directly, so changes to the variable will reflect in the lambda.

What happens if the captured variable goes out of scope?

If a captured variable goes out of scope and the lambda is still in use, it leads to undefined behavior. It's important to ensure that the lifetime of captured variables extends beyond the lambda's usage.

Can you provide a code snippet demonstrating both capture methods?

Certainly! Here's a simple example:

#include <iostream>
#include <vector>

int main() {
    int a = 10;
    int b = 20;

    auto byValue = [a]() { return a + 5; };
    auto byReference = [&b]() { b += 5; };

    std::cout << "By Value: " << byValue() << std::endl; // Outputs 15
    byReference();
    std::cout << "By Reference: " << b << std::endl; // Outputs 25
}

This demonstrates capturing by value and by reference.