How can I implement custom functions in C++ standard algorithms?

How can I implement custom functions in C++ standard algorithms?

You can implement custom functions by using function pointers or functors. Would you like an example?

Yes, please provide an example of using a functor.

Sure! Here's a simple functor that adds a value to each element in a vector:

struct AddValue {
    int value;
    AddValue(int v) : value(v) {}
    int operator()(int x) const { return x + value; }
};

You can use it with std::transform like this:

std::vector<int> vec = {1, 2, 3};
std::transform(vec.begin(), vec.end(), vec.begin(), AddValue(5));

This will add 5 to each element.

That's great! Can I use lambda functions instead?

Absolutely! You can use lambda functions for a more concise syntax. Here's how you can do it:

std::vector<int> vec = {1, 2, 3};
std::transform(vec.begin(), vec.end(), vec.begin(), [](int x) { return x + 5; });

This will achieve the same result.

Thanks! What about using custom comparison functions with sorting?

You can use custom comparison functions with std::sort as well. Just pass a lambda or a functor as the third argument to std::sort.