第五章 數組
1. 動態創建數組時，不能進行初始化，但卻可以用值初始化() 要求編譯器把內置類型初始化爲0
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int
*
pia2
=
new
int
[
10
]();
// ok: array of 10 initialized ints with value 0
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@font-face
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mso-generic-font-family:auto;
mso-font-pitch:variable;
mso-font-signature:3 135135232 16 0 262145 0;}
@font-face
{font-family:新宋體;
panose-1:2 1 6 9 3 1 1 1 1 1;
mso-font-charset:134;
mso-generic-font-family:modern;
mso-font-pitch:fixed;
mso-font-signature:3 135135232 16 0 262145 0;}
@font-face
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panose-1:2 1 6 9 3 1 1 1 1 1;
mso-font-charset:134;
mso-generic-font-family:modern;
mso-font-pitch:fixed;
mso-font-signature:3 135135232 16 0 262145 0;}
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{mso-style-parent:"";
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delete
[]
pia1
;
2. 指針的初始化和賦值：
指針的初始化或賦值只能是下面四種：
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@page
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1
）0
常量表達式；
2
）類型匹配的對象的地址；
3
）另一對象末的下一個地址；
4
）同一類型的另一個有效指針。
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這裏需要舉一個例子：
typedef string* pstring;
const pstring cstr;
請問 cstr
是什麼類型？
這是一個很容易答錯的問題。實質上cstr
是一個string*
類型的const
變量，即上面的定義相當於
string* const cstr;
因爲聲明const pstring cstr;
時，const
修飾的是pstring
的類型，而不是修飾string
類型。
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第六章 表達式
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1. sizeof
操作符
的作用是返回對象或類型名的長度，返回值的類型爲size_t
，長度的單位是字節。sizeof
表達式的結果是編譯時常量，具有三種形式：
sizeof (type name);
sizeof (expr);
sizeof expr;
2.new和delete
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當刪除指針所指對象後，該指針就變爲所謂的懸垂指針，其指向了一個已經被刪除的對象的位置。
建議：當刪除了指針所指對象後，應當立即將指針置0
。