本文详细介绍了C++中数组的动态创建及初始化方法，包括不同方式下数组元素的默认值设定。同时探讨了指针的初始化和赋值规则，并通过具体示例解释了类型修饰符const的应用。
第五章 数组
1. 动态创建数组时，不能进行初始化，但却可以用值初始化() 要求编译器把内置类型初始化为0
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int
*
pia2
=
new
int
[
10
]();
// ok: array of 10 initialized ints with value 0
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delete
[]
pia1
;
2. 指针的初始化和赋值：
指针的初始化或赋值只能是下面四种：
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1
）0
常量表达式；
2
）类型匹配的对象的地址；
3
）另一对象末的下一个地址；
4
）同一类型的另一个有效指针。
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这里需要举一个例子：
typedef string* pstring;
const pstring cstr;
请问 cstr
是什么类型？
这是一个很容易答错的问题。实质上cstr
是一个string*
类型的const
变量，即上面的定义相当于
string* const cstr;
因为声明const pstring cstr;
时，const
修饰的是pstring
的类型，而不是修饰string
类型。
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第六章 表达式
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1. sizeof
操作符
的作用是返回对象或类型名的长度，返回值的类型为size_t
，长度的单位是字节。sizeof
表达式的结果是编译时常量，具有三种形式：
sizeof (type name);
sizeof (expr);
sizeof expr;
2.new和delete
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当删除指针所指对象后，该指针就变为所谓的悬垂指针，其指向了一个已经被删除的对象的位置。
建议：当删除了指针所指对象后，应当立即将指针置0
。
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