Closures and Higher-Order Functions

Closures and Higher-Order Functions

In this lesson — part of Advanced Features — you'll learn closures and higher-order functions in C++ and why it matters in real work.

Why it matters

Functions that take or return functions unlock concise, composable code.

Key ideas

• Functions as values
• map / filter / reduce
• Callbacks
• Composition

In practice

Here's how it looks in idiomatic C++:

#include <vector>
#include <algorithm>
#include <iterator>
std::vector<int> nums{1, 2, 3, 4, 5};
std::vector<int> doubled, evens;
std::transform(nums.begin(), nums.end(), std::back_inserter(doubled),
               [](int n){ return n * 2; });          // map
std::copy_if(nums.begin(), nums.end(), std::back_inserter(evens),
             [](int n){ return n % 2 == 0; });         // filter

C++ note: The <algorithm> library provides higher-order operations: std::transform is map and std::copy_if is filter, both taking lambdas; C++20 ranges offer a composable nums | views::filter(...) pipeline syntax.

Try it yourself

Exercise: In C++, use map and filter to get the squares of the even numbers.

Recap

You now understand closures and higher-order functions and can apply it in C++. Mark this lesson complete and continue to the next one.