Once you have values in a container, you can call functions to get information about those items. The count function is used to count the number items with a specified value in a range:

    vector<int> planck{ 6,6,2,6,0,7,0,0,4,0 }; 
    auto number = count(planck.begin(), planck.end(), 6);

This code will return a value of 3 because there are three copies of 6 in the container. The return type of the function is the type specified in the difference_typetypedef of the container, and in this case it will be int. The count_if function works in a similar way, but you pass a predicate that takes a single parameter (the current item in the container) and returns a bool specifying if this is the value that is being counted.

The count functions count the number of occurrences of a specific value. If you want to aggregate all the values, then you can use the accumulate function in <numeric>. This will iterate over the range, access each item and keep a running sum of all the items.

The sum will be carried out using the + operator of the type, but there is also a version that takes a binary function (two parameters of the container type and returns the same type) that specifies what happens when you add two such types together.

The all_of, any_of, and none_of functions are passed a predicate with a single argument of the same type of the container; there are also given iterators indicating a range over which they iterate, testing each item with the predicate. The all_of function will return true only if the predicate is true for all items, the any_of function returns true if predicate is true for at least one of the items, and the none_of function will return true only if the predicate is false for all items.