LambdaProblem

#include <iostream>
#include <algorithm>

int reduce(long ar[], int n);

int main()
{
    long tab[] = {5, 3, 5, 6, 8, 2, 1, 3, 2, 8, 6, 1, 7};

    int size = reduce(tab, 13);

    return 0;
}

int reduce(long ar[], int n)
{
    std::sort(ar, ar+n);
    int size{};
    std::for_each(ar, std::unique(ar, ar+n), [&](){++size;}); // dlaczego tutaj lambda krzyczy błąd???
    return size;
}