SGI slist和C ++ 11 forward_list有什么区别? [英] What is the difference between SGI slist and C++11 forward_list?

问题描述

除非我错过了某些内容，否则SGI slist和C ++ 11 std::forward_list都与我相同.两者都实现一个单链列表.

Both SGI slist and C++11 std::forward_list appear identical to me unless I have missed something; both implement a singly-linked list.

我认为这是有区别的，因为C ++标准委员会在将容器添加到C ++ 0x标准库中时没有采用名称slist而是选择了新名称forward_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.

推荐答案

一个主要区别是std::forward_list缺少size()成员函数，而sgi::slist则没有.这样做的动机是O(N)size()存在问题. N2543 有关设计的更多详细信息forward_list的决定.

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.

更新:

我最近有一个很好的借口来更仔细地研究这个主题. slist还有其他成员函数，很容易想到它们是O(1)，但实际上是O(N).这些包括:

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);

简而言之，如果您非常不太谨慎，则使用slist可能会导致严重的性能问题.使用std::forward_list可以确保您从单链列表中获得预期的O(1)性能.

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.

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