Beginners Programming Challenge #20

[schauerlich]

Huh, I should probably pick a winner. I'll wait for mo.reina to finish, though.

[mo.reina]

all done.

[schauerlich]

Alright! Sorry it's taken so long to pick a winner for this, school tends to be distracting.

Anyways, the winning entry belong to jwbrase! His Haskell entry was concise, functional (in both senses of the word), and implemented the other functions in terms of reduce. Thank you to all of the participants, and congratulations jwbrase! We'll be looking out for the next challenge.

[schauerlich]

jwbrase has let me know he can't run the next challenge at the moment - is there anyone else interested in hosting it?

[Queue29]

jwbrase has let me know he can't run the next challenge at the moment - is there anyone else interested in hosting it?

I'd be happy to do it

[schauerlich]

I'd be happy to do it

Alright. Unless someone from the beginner's team objects, go ahead and make the next one!

[ziekfiguur]

I know the challenge is officially over, but i saw noone gave a C++ solution, so i thought i should give it a try (and refresh my template skills which i haven't used for a long time).

#include <iostream>
#include <vector>

template <typename Function, typename T>
std::vector<T> map(Function f, std::vector<T> const &data)
{
    std::vector<T> result;
    for (typename std::vector<T>::const_iterator it = data.begin();
            it != data.end();
                ++it)
        result.push_back(f(*it));
    return result;
}

template <typename T>
class Square
{
    public:
        T operator()(T const &x)
        {
            return x * x;
        }
};

template <typename Function, typename T>
std::vector<T> filter(Function f, std::vector<T> const &data)
{
    std::vector<T> result;
    for (typename std::vector<T>::const_iterator it = data.begin();
            it != data.end();
                ++it)
        if (f(*it))
            result.push_back(*it);
    return result;
}

class isOdd
{
    public:
        int operator()(int x)
        {
            return x & 1;
        }
};

template <typename Function, typename T>
T reduce(Function f, std::vector<T> const & data, T const &i)
{
    T value = i;
    for (typename std::vector<T>::const_iterator it = data.begin();
            it != data.end();
                ++it)
            value = f(value, *it);
    return value;
}

template <typename T>
class add
{
    public:
        T operator()(T const &v1, T const &v2)
        {
            return v1 + v2;
        }
};

template <typename T>
void print(std::vector<T> const &data)
{
    for (typename std::vector<T>::const_iterator it = data.begin();
            it != data.end();
                ++it)
        std::cout << *it << ' ';
    std::cout << '\n';
}

int main()
{
    int array[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    std::vector<int> vec(array, array + 10);

    std::vector<int> squares = map(Square<int>(), vec);
    print(squares);

    std::vector<int> odds = filter(isOdd(), vec);
    print(odds);

    std::vector<int> vec2(array, array + 5);
    int sum = reduce(add<int>(), vec2, 0);
    std::cout << sum << std::endl;
    return 0;
}