Functional map/filter C++

#include <iostream>
#include <vector>
#include <algorithm>
#include <type_traits>

using namespace std;

/*
Terminology - callback : A function passed as a parameter to another function
*/


//Returns an array based off the input array manipulated by the callback
template <class Container, class Funktion>
auto _map (const Container &cont, Funktion fun) {
    std::vector<typename std::result_of<Funktion(const typename Container::value_type&)>::type> ret;
    for (const auto &v : cont) {
        ret.push_back(fun(v));
    }
    return ret;
}

//Filters higher function, utilizes C++' remove_if function
template <typename Collection,typename Predicate>
Collection filterNot(Collection col,Predicate predicate ) {
    auto returnIterator = std::remove_if(col.begin(),col.end(),predicate);
    col.erase(returnIterator,std::end(col));
    return col;
}

//Uses filterNot with a NOT operator and returns an array of which the elements from the input array are passed to the callback and return true.
template <typename Collection,typename Predicate>
Collection filter(Collection col,Predicate predicate) {
 //capture the predicate in order to be used inside function
 auto fnCol = filterNot(col,[predicate](typename Collection::value_type i) { return !predicate(i);});
 return fnCol;
}

//Prints anything passed to it
template <class T>
void printEverything( std::vector<T> vec )
{
    for( typename std::vector<T>::iterator iter = vec.begin();  iter != vec.end(); ++iter )
    {
        std::cout << *iter << std::endl ;
    }
}

int square(int a){
    return a * a;
}

//If the remainder of x / 2 is 0, the number is even therefore returns true
bool isEven(int x){
    return x % 2 == 0;
}

int main()
{
    /*
    // playing with lambda expressions
    auto func = [] () { std::cout << "Hello World\n"; };
    func();
    int result = [](int input) -> int {return 2 * input; }(10);
    std::cout << result << std::endl;
    int otherResult = [](int a,int b) -> int { return a + b; }(2,4);
    */

    std::vector<int> input({4,6,7,8,9});
    auto squaredNumbersArray =_map(input, square);
    auto evenNumbersArray = filter(input, isEven);
    printEverything(squaredNumbersArray);
    printEverything(evenNumbersArray);
    return 0;
}