24 Containers library [containers]

24.3 Sequence containers [sequences]

24.3.9 Class template forward_list [forward.list] Iterators [forward.list.iter]

iterator before_begin() noexcept; const_iterator before_begin() const noexcept; const_iterator cbefore_begin() const noexcept;
Effects: cbefore_begin() is equivalent to const_cast<forward_list const&>(*this).before_begin().
Returns: A non-dereferenceable iterator that, when incremented, is equal to the iterator returned by begin().
Remarks: before_begin() == end() shall equal false.