Why wasn't std::forward_list given a count() member function?
c++, c++11, containers, forward-list, stl
Solution
The member functions you mention (`merge()`, `reverse()`, `remove()`, `remove_if()`, `unique()`, `sort()`) are provided because they have better complexity than the generic algorithms in the `<algorithm>` standard headers.
A member function such as `count()`, on the other hand, would not have better complexity than `std::distance(std::begin(some_list), std::end(some_list))`.
Also, it may be misinterpreted as the better-complexity version of the `std::count` generic algorithm, which does something basically different.
Problem
I understand why `std::forward_list` does not have a `size()` member function, since an `O(1)` version would mess up the complexity of certain `splice()` overloads, and since an `O(N)` version would be inconsistent with all the rest of the Standard Library's containers. It is also true that both `std::list` and `std::forward_list` already have several other member functions with the same semantics as their cousins from the `<algorithm>` corner of the Standard Library (`merge()`, `reverse()`, `remove()`, `remove_if()`, `unique()`, `sort()`). So why wasn't a `count()` member function of `O(N)` complexity provided to `std::forward_list` that had the semantics of returning `std::distance(std::begin(some_list), std::end(some_list))`?