August 2021
Intermediate to advanced
450 pages
9h 36m
Chinese
Content preview from C++程序设计：原理与实践（基础篇）（原书第2版）
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8.2.2 变量和常量声明
一个变量或常量声明指定一个名字和一个类型，并可进行初始化。例如：
你可在ISO C++标准中找到完整语法。
常量声明的语法与变量声明一样，差别在于类型之前多了一个关键字const，而且必须进行初始化：
必须进行初始化的原因是显然的：如果一个常量没有值的话，它何以为常量呢？对变量也进行初始化通常是个好主意，未初始化的变量常会导致隐蔽的错误。例如：
这段代码看起来再正常不过，但如果在第一个“…”处包含对x的使用又如何呢？例如：
因为x未初始化，所以执行z>x的结果是未定义的。在不同的机器平台上，比较操作z>x会给出不同的结果，甚至同一台机器上执行多次也会给出不同的结果。原则上，z>x应导致程序因一个硬件错误而终止，但多数时候这不会发生，取而代之的是我们会得到一个不可预知的结果。 ...
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