Is it possible to erase elements of a std::list in a c++11 for each loop

Question

I want to use the new C++11 for each loop to iterate over all elements of a list and erase certains elements. For example

std::list<int> myList;
myList.push_back(1); 
myList.push_back(13);
myList.push_back(9);
myList.push_back(4);

for(int element : myList) {
    if(element > 5) {
        //Do something with the element

        //erase the element
    }else{
        //Do something else with the element
    }
}

Is it possible to do this using the for each loop or do I have to go back to iterators to achive this?

Answer 1

You should be able to just do this

myList.erase(std::remove_if(myList.begin(), myList.end(),
    [](int& element) 
    { 
        return element > 5;
    } 
    ),myList.end());

or simply (courtesy Benjamin Lindley)

myList.remove_if(
    [](int& element) 
    { 
        return element > 5;
    } 
    );

Answer 2

You can't erase elements of standard containers in a range-based for loop over that container -- the loop itself has an iterator to the element that you're currently visiting, and erasing it would invalidate that iterator before the loop increments it.

Range-based for is defined in 6.5.4 of the standard to be equivalent to (slightly simplified):

for (auto __begin=begin-expr, __end=end-expr; __begin != __end; ++__begin) {
    for-range-declaration = *__begin;
    statement
}

begin-expr and end-expr have their own lengthy definition, but in your example they are myList.begin() and myList.end() respectively.