Copying Algorithms

Copying from Generated Ranges

Can these copy algorithms be used with input ranges that are generated on-the-fly, such as from a generator function?

Yes, these copy algorithms can be used with input ranges that are generated on-the-fly, such as from a generator function. The key is to create an iterator that generates values as needed and supports the necessary iteratorÂ interface.

Generator Function

Hereâ€™s an example of a generator function that produces an infinite sequence of numbers, and how you can use it with std::ranges::copy_n():

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

class InfiniteSequence {
public:
InfiniteSequence(int start) : current(start) {}

int operator()() {
return current++;
}

private:
int current;
};

int main() {
InfiniteSequence generator(1);
std::vector<int> Destination(10);

std::generate_n(
Destination.begin(), 10, generator);

for (int Value : Destination) {
std::cout << Value << ", ";
}
}
1, 2, 3, 4, 5, 6, 7, 8, 9, 10,

Using Custom Iterators

To create an input range that can be used with std::ranges::copy() or other algorithms, you can define a custom iterator that generates values on-the-fly. Hereâ€™s anÂ example:

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

class GeneratorIterator {
public:
using iterator_category = std::input_iterator_tag;
using value_type = int;
using difference_type = std::ptrdiff_t;
using pointer = int*;
using reference = int&;

GeneratorIterator(int start) : current(start) {}

int operator*() const { return current; }
GeneratorIterator& operator++() {
++current;
return *this;
}

GeneratorIterator operator++(int) {
GeneratorIterator tmp = *this;
++current;
return tmp;
}

friend bool operator==(const GeneratorIterator& a,
const GeneratorIterator& b) {
return a.current == b.current;
}

friend bool operator!=(const GeneratorIterator& a,
const GeneratorIterator& b) {
return a.current != b.current;
}

private:
int current;
};

int main() {
GeneratorIterator start(1);
GeneratorIterator end(11);  // End after generating 10 elements
std::vector<int> Destination(10);

std::copy(start, end, Destination.begin());

for (int Value : Destination) {
std::cout << Value << ", ";
}
}
1, 2, 3, 4, 5, 6, 7, 8, 9, 10,

Using a Generator Function Directly with std::ranges::copy()

You can also use a generator function directly with std::ranges::copy() by converting it into a range. Hereâ€™sÂ how:

#include <algorithm>
#include <iostream>
#include <vector>
#include <ranges>
#include <iterator>

auto generate_infinite_sequence(int start) {
return std::views::iota(start);
}

int main() {
auto generator = generate_infinite_sequence(1);
std::vector<int> Destination(10);

std::ranges::copy_n(
generator.begin(), 10, Destination.begin());

for (int Value : Destination) {
std::cout << Value << ", ";
}
}
1, 2, 3, 4, 5, 6, 7, 8, 9, 10,

Key Points

• Custom Iterators: Define custom iterators to generate values on-the-fly.
• Compatibility: Ensure the iterator supports the necessary interface (operator*, operator++, and operator!=).
• Flexibility: This approach allows you to generate values dynamically and use them with standard copy algorithms.

By using generator functions or custom iterators, you can effectively integrate on-the-fly input ranges with standard copy algorithms, making your code more flexible andÂ powerful.

This Question is from the Lesson:

Copying Algorithms

An introduction to the 7 copying algorithms in the C++ standard library: copy(), copy_n(), copy_if(), copy_backward(), reverse_copy(), rotate_copy(), and unique_copy().

Answers to questions are automatically generated and may not have been reviewed.

This Question is from the Lesson:

Copying Algorithms

An introduction to the 7 copying algorithms in the C++ standard library: copy(), copy_n(), copy_if(), copy_backward(), reverse_copy(), rotate_copy(), and unique_copy().

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