заменить отрицательные елементы массива

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
#include <functional>
#include <cstdlib>
#include <ctime>
 
double positive_average(const std::vector<double> & vec){
    double sum = 0.0;
    size_t count = 0;
    
    for ( std::vector<double>::const_iterator i = vec.begin(); i != vec.end(); ++i )
        if ( *i > 0.0 && ++count )
            sum += *i;
    
    return ( count ) ? sum / static_cast<double>(count) : 0.0;
}
 
template <typename T>
class RandNumber {
    int lo;
    int hi;
public:
    RandNumber(int Lo, int Hi): lo(Lo), hi(Hi) {}
    T operator () (){
        return static_cast<T>( rand() % (hi - lo + 1) + lo );
    }
};
 
int main(){
    const int SIZE(10);
    const int LO(-200);
    const int HI(200);
    
    std::vector<double> vec(SIZE);
    srand(time(NULL));
    std::generate(vec.begin(), vec.end(), RandNumber<double>(LO, HI));
    
    std::cout << "ARRAY:   ";
    std::copy(vec.begin(), vec.end(), std::ostream_iterator<double>(std::cout, " "));
    std::cout << std::endl;
    
    double avg = positive_average(vec);
    if ( avg > 0.0 ){
        std::cout << "Average of positive elements: " << avg << std::endl;
        std::replace_if(vec.begin(), vec.end(), std::bind2nd(std::less<double>(), 0.0), avg);
        std::cout <<"CHANGED: ";
        std::copy(vec.begin(), vec.end(), std::ostream_iterator<double>(std::cout, " "));
        std::cout << std::endl;
    }
    
    return 0;
}

#include <iostream>
#include <algorithm>
#include <iterator>
#include <functional>
#include <array>
#include <random>
#include <ctime>
 
int main()
{
    typedef std::ostream_iterator<int> int_out_iter;
 
    auto rand_generator = std::bind(std::uniform_int_distribution<int>(-100, 100),
                                    std::mt19937(std::time(nullptr)));
 
    std::array<int, 100> a;
    std::generate(a.begin(), a.end(), rand_generator);
 
    std::copy(a.begin(), a.end(), int_out_iter(std::cout, " "));
    std::cout << '\n';
 
    int sum = 0;
    std::for_each(a.begin(), a.end(), [&sum](int i) { if(i > 0) sum+= i; });
 
    int pos_average = sum / a.size();
    std::replace_if(a.begin(), a.end(), [](int i) { return i < 0; }, pos_average);
 
    std::copy(a.begin(), a.end(), int_out_iter(std::cout, "  "));
    std::cout << '\n';
 
    return 0;
}