April 2018
Intermediate to advanced
303 pages
4h 54m
Chinese
Content preview from Effective Modern C++（中文版）
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46
｜
第
2
章
不是什么新鲜事，而只是采纳了在其他编程语言中称为型别推导的东西而已。其他的
静态型别过程式语言（如
C#
、
D
、
Scala
、
Visual Basic
）中或多或少都有这么一个等
价的特性，更不用说一系列静态型别函数式语言（如
ML
、
Haskell
、
OCaml
、
F#
等）。
这些语言之所以要引入如此特性，部分原因在于动态型别语言的成功，而在后者中变
量很少有显式型别。软件开发社区已经积累了丰富的型别推导方面的经验，而这也说
明此类技术并不会与撰写和维护大型的、工业强度的基础代码这样的工作产生冲突。
有些程序员会觉得使用了
auto
以后，就不能一眼从源代码中看出对象的型别，因而
感觉烦恼。但是，
IDE
的对象型别显示能力往往会缓和这个问题（即使考虑到条款
4
中提及的
IDE
的型别显示缺陷），并且，在很多情况下，对于对象型别的抽象理解可
能和了解它的精确型别同等有用。比如说，知道某个对象是个容器、是个计数器，还
是个智能指针就已经够用了，没有必要了解它具体是哪种型别的容器、计数器或智能
指针。如果再取个好一点的变量名字，那么一些抽象型别信息就近乎总是唾手可得了。
事实上，显式地写出型别经常是画蛇添足，带来各种微妙的偏差，有些关乎正确性，
有些关乎效率，或是两者都受影响。还有，
auto
型别可以随着其初始化表达式的型别
变化而自动随之改变，这就意味着通过使用
auto
，有一些重构动作就被顺手做掉了。
例如，假设有一个函数本来声明的返回型别是
int
，但后来又觉得
long
更合适一些，
那么如果函数调用的结果是存储在
auto ...
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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.