/* Chaining operations by overloading bitwise OR ('|') operator. Given a vector v = {1,2,3,4,5,6,7,8,9,10,11,12}, first Filter is applied to remove all elements <= 4, which leaves v = {5,6,7,8,9,10,11,12}, then Transform is applied to double the value of all elements, which makes v v = {10,12,14,16,18,20,22,24}. The again filter is applied to remove all elements divisible by 3, so we have our final vector v = {10, 14, 16, 20, 22 }. Again a Transform operation double the values is applied. This time it modifies the container instead of creating a new one producing the results 20,28,32,40,44 */ #include #include #include using namespace std; template struct pipe_func { F f; template friend auto operator|(Lhs&& lhs, pipe_func rhs ) { return rhs.f(forward(lhs)); } template friend auto&& operator |= (Lhs&& lhs, pipe_func rhs) { lhs = rhs.f(forward(lhs)); return lhs; } }; // helper forward declaration template pipe_func(F)->pipe_func; //Filter returns a pipe function containing a lambda function that will apply std::remove_copy_if to the source container and returns a new target container of same type containing the filtered elements by applying the predicate P auto Filter = [](auto P) { return pipe_func{[=](auto&& source) { using T = decay_t; T target; remove_copy_if(begin(source), end(source), back_inserter(target), P); return target; }}; }; //Transform returns a pipe function containing a lambda function that will apply std::transform to the source container and returns a new target container of same type containing the transformed elements by applying the predicate P auto Transform = [](auto P) { return pipe_func{[=](auto&& source) { using T = decay_t; T target; transform(begin(source),end(source), back_inserter(target), P); return target; }}; }; int main() { std::vector vdata{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}; auto DoubleIt = [](int v) { return v * 2; }; auto Remove_Lteq4 = [](auto v) { return v <= 4; }; auto Remove_divideby3=[](auto v) { return !(v % 3); }; std::vector test1 = vdata | Filter(Remove_Lteq4) | Transform(DoubleIt) | Filter(Remove_divideby3); // output for (auto v : test1) std::cout << v << " "; std::cout << "\n"; //transform it once more test1 |= Transform(DoubleIt); // output for (auto v : test1) std::cout << v << " "; std::cout << "\n"; }

Chaining_operations_using_overloading.cpp