April 2018
Intermediate to advanced
303 pages
4h 54m
Chinese
Content preview from Effective Modern C++（中文版）
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41
第
2
章
auto
如果单从概念上看，
auto
真是简单到不能再简单，然而细究起来里面却大有文章。使
用
auto
可以少打一些字，没错，但好处不止这些：它还能阻止那些由于手动指定型别
带来的潜在错误和性能问题。还有，某些
auto
型别推导结果尽管是按部就班地符合标
准规定的推导算法，然而从程序员的视角来看却是错误的。如果是这样的情况，那就
很有必要知道如何去引导
auto
得出正确结果，因为退回手工指定型别的声明，是通常
需要避免的途径。
这个小小的章节讨论了有关
auto
的一切。
条款
5
：优先选用
auto
，而非显式型别声明
啊，下面这个语句多么天真无邪：
int x;
等等，我忘记初始化
x
了，所以它的值是不确定的。不过也不一定，它也许被初始化
为零了。到底怎样全看具体语境。
别烦恼。我们可以再看一个天真无邪的例子，使用迭代器的提领结果来初始化局部变
量：
template<typename It>
// dwim
（做我所想，
do what I mean
）算法
void dwim(It b, It e)
//
应用范围是从
b
到
e
的所有元素
{
while (b != e) {
typename std::iterator_traits<It>::value_type
currValue = *b;
42
｜
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.