copy_ifExample

#include <iostream>

template <typename T>
void forEach(T* arrB, T* arrE, void(*action)(T& el))
{
    while (arrB != arrE)
    {
        if (action) { action(*arrB++); };
    }
}

void printElement(int& el)
{
    std::cout << el << ' ';
};

template <typename T>
int copy_if(T* srcB, T* srcE, T* destB, T* destE, bool(*pred)(T& elem))
{
    int copyCount{ 0 };
    while (destB != destE and srcB != srcE)
    {
        if (pred(*srcB))
        {
            *destB++ = *srcB;
            ++copyCount;
        }
        ++srcB;
    }
    return copyCount;
}

bool trueer(int& el)
{
    return true;
}

bool falseer(int& el)
{
    return false;
}

bool evener(int& el)
{
    return !(el % 2);
}

bool odder(int& el)
{
    return (el % 2);
}

bool greater5(int& el)
{
    return el > 5;
}

int main()
{
    const int size{ 10 };
    int arr[size]{ 1,2,3,4,5,6,7,8,9,10 };
    int* arrBegin{ arr };
    int* arrEnd{ arr + size };

    const int size1{ 3 };
    int arr1[size1]{};
    int* arr1Begin{ arr1 };
    int* arr1End{ arr1 + size1 };

    int copyCount{ 0 };

    forEach(arrBegin, arrEnd, printElement);
    std::cout << '\n';
    forEach(arr1Begin, arr1End, printElement);
    std::cout << '\n';
    copyCount = copy_if(arrBegin, arrEnd, arr1Begin, arr1End, greater5);
    forEach(arr1Begin, arr1End, printElement);
    std::cout << '\n' << copyCount << " elements copied\n";
    std::cout << '\n';
}