template<class T, class Allocator, class U = T> constexpr typename forward_list<T, Allocator>::size_type erase(forward_list<T, Allocator>& c, const U& value);
template<class T, class Allocator, class Predicate> constexpr typename forward_list<T, Allocator>::size_type erase_if(forward_list<T, Allocator>& c, Predicate pred);