23 Containers library [containers]

23.3 Sequence containers [sequences]

23.3.7 Class template forward_list [forward.list]

23.3.7.3 Iterators [forward.list.iter]

constexpr iterator before_begin() noexcept;
constexpr const_iterator before_begin() const noexcept;
constexpr 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.