In C++, a closure can be implemented using lambda expressions. A closure is a function object that has access to variables local to the scope in which it was defined.
Here's an example of using closure in C++:
``c++
#include
#include
#include
int main() {
std::vector
int count = 0; // a variable local to the main function
std::for_each(numbers.begin(), numbers.end(), [&count](int n) { // using lambda expression
if (n % 2 == 0) {
count++;
}
});
std::cout << "The number of even numbers in the vector is: " << count << std::endl;
return 0;
}
`
In this example, we use std::for_each() algorithm to iterate through a vector of integers and count how many even numbers are there. The closure, which is the lambda expression [&count](int n) { ... }, captures the count variable from the main function's scope and increments it every time it encounters an even number in the vector.
The square brackets [&count] indicate that we want to capture count by reference so its value can be modified by the closure.
This is just a simple example but closures are particularly useful when working with algorithms that require a function object as a parameter, such as std::sort() or std::transform()`.