Looping Over Vectors

Often we will want to loop over the elements contained in a vector, and C++ provides a range-based loop for this purpose. For example to loop over all elements and output them to the terminal, we could do:

for (auto e : container) {
    std::cout << e << std::endl;
}

Here we see a new keyword, auto. Each pass through this loop, e will take on the next value in our vector called container. The body of the loop is contained in the {...}.

C++ requires that we declare the data type of e. In this case, the compiler knows that it will have to be a double, since the vector is a vector of double, so we can use the auto keyword to have the compiler automatically deduce the data type.

try it…

Let’s add a loop to our code and compute the average of the elements in the vector.