Impara Function Composition | Working with Predicates and Algorithms

Function composition is a powerful technique that lets you combine multiple functions or predicates to build more complex operations from simpler ones. In C++, you can achieve function composition and chaining by using lambdas and standard algorithms. This approach is especially useful when you want to apply a series of transformations or filters to collections, such as vectors, in a concise and expressive way.

main.cpp


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#include <iostream>
#include <vector>
#include <algorithm>

int main()
{
    std::vector<int> numbers{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    // First lambda: filter even numbers
    auto is_even = [](int x) { return x % 2 == 0; };

    // Second lambda: square a number
    auto square = [](int x) { return x * x; };

    // Compose: filter then transform
    std::vector<int> evens;
    std::copy_if(numbers.begin(), numbers.end(), std::back_inserter(evens), is_even);

    std::vector<int> squared_evens;
    std::transform(evens.begin(), evens.end(), std::back_inserter(squared_evens), square);

    std::cout << "Squared even numbers: ";
    for (int n : squared_evens)
        std::cout << n << " ";
    std::cout << std::endl;
}

By composing functions, you can create pipelines where the output of one function becomes the input of the next, making your code modular and easier to maintain.

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Sezione 2. Capitolo 4

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main.cpp


              1234567891011121314151617181920212223242526
            
#include <iostream>
#include <vector>
#include <algorithm>

int main()
{
    std::vector<int> numbers{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    // First lambda: filter even numbers
    auto is_even = [](int x) { return x % 2 == 0; };

    // Second lambda: square a number
    auto square = [](int x) { return x * x; };

    // Compose: filter then transform
    std::vector<int> evens;
    std::copy_if(numbers.begin(), numbers.end(), std::back_inserter(evens), is_even);

    std::vector<int> squared_evens;
    std::transform(evens.begin(), evens.end(), std::back_inserter(squared_evens), square);

    std::cout << "Squared even numbers: ";
    for (int n : squared_evens)
        std::cout << n << " ";
    std::cout << std::endl;
}

By composing functions, you can create pipelines where the output of one function becomes the input of the next, making your code modular and easier to maintain.

Tutto è chiaro?

Grazie per i tuoi commenti!

Sezione 2. Capitolo 4