问题
Both SGI slist
and C++11 std::forward_list
appear identical to me unless I have missed something; both implement a singly-linked list.
I assume there is a difference though as the C++ Standard Commitee didn't adopt the name slist and instead chose a new name, forward_list, when they added the container into the Standard Library for C++0x.
回答1:
One major difference is that std::forward_list
lacks a size()
member function, where as the sgi::slist
doesn't. The motivation for this is that an O(N) size()
has been problematic. N2543 has more details on the design decisions for forward_list
.
Update:
I recently had a good excuse to look closer at this subject. slist
also has other member functions that one would be tempted to think are O(1), but are really O(N). These include:
iterator previous(iterator pos);
const_iterator previous(const_iterator pos) const;
iterator insert(iterator pos, const value_type& x);
iterator erase(iterator pos);
void splice(iterator position, slist& x);
void splice(iterator position, slist& x, iterator i);
In short, if you're not very careful, you can end up with significant performance problems by using slist
. Use of std::forward_list
instead ensures that you'll get the expected O(1) performance out of your singly linked list.
回答2:
So put simply, sgi::slist and forward_list are very similar.
The differences being that forward_list lacks a size() member function which is included in sgi::slist and forward_list includes an emplace_after member function which isn't included in sgi::slist. Also, forward_list doesn't provide insert and erase member functions like sgi::slist does.
If you know of any other differences, please don't hesitate to mention them.
回答3:
I've recently run into another difference. The method splice_after
has a different interface and different behaviour.
1) forward_list Requires you to pass the container you're moving from as a second argument:
void splice_after( const_iterator pos, forward_list& other,
const_iterator first, const_iterator last );
slist:
void splice_after(iterator pos, iterator before_first, iterator before_last)
This is similar for the overloads.
2) Specific for the overload mentioned above: the last iterator is interpreted differently! Where slist moves the range [ before_first + 1, before_last + 1 >, forward_list moves the range < first, last >. So, when converting code (since slist is deprecated in GCC, for instance), make sure to use: last = before_last + 1.
来源:https://stackoverflow.com/questions/6885436/what-is-the-difference-between-sgi-slist-and-c11-forward-list