Process for each adjacent pair in collection

adjacent_pair.cpp

#include <iostream>
#include <vector>

// process for each adjacent pair in collection:
// [2, 3, 5, 7, 9] ==> f(2, 3), f(3, 5), f(5, 7), f(7, 9)
template <typename Iter, typename Func>
void adjacent_pair(Iter first, Iter last, Func f) {
    auto trailer = first;
    first++;
    while (first != last) {
        f(*trailer, *first);
        first++;
        trailer++;
    }
}

struct PairPrinter {
    void operator()(int a, int b) {
        std::cout << "(" << a << "," << b << "), ";
    }
};

void PairPrinterF(int a, int b) { std::cout << "f(" << a << "," << b << "), "; }

int main(int argc, char *argv[]) {
    std::vector<int> foo = {2, 3, 5, 7, 9};
    for (auto i : foo) std::cout << i << " ";
    std::cout << std::endl;

    adjacent_pair(foo.begin(), foo.end(), PairPrinterF);
    std::cout << std::endl;

    adjacent_pair(foo.begin(), foo.end(), [](int a, int b) {
        std::cout << "l(" << a << "," << b << "), ";
    });
    std::cout << std::endl;

    return 0;
}