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闃呰鍏ㄦ枃
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闈欐佽仈緙?
闈欐佽仈緙栨槸鎸囪仈緙栧伐浣滃嚭鐜板湪緙栬瘧榪炴帴闃舵錛岃繖縐嶈仈緙栧張縐版棭鏈熻仈緙栵紝鍥犱負榪欑鑱旂紪榪囩▼鏄湪紼嬪簭寮濮嬭繍琛屼箣鍓嶅畬鎴愮殑銆?
鍦ㄧ紪璇戞椂鎵榪涜鐨勮繖縐嶈仈緙栧張縐伴潤鎬佹潫瀹氥傚湪緙栬瘧鏃跺氨瑙ｅ喅浜嗙▼搴忎腑鐨勬搷浣滆皟鐢ㄤ笌鎵ц璇ユ搷浣滀唬鐮侀棿鐨勫叧緋伙紝紜畾榪欑鍏崇郴鍙堢О涓烘潫瀹氾紝鍦ㄧ紪璇戞椂鏉熷畾鍙堢О闈欐佹潫瀹氥備笅闈婦涓涓潤鎬佽仈緙栫殑渚嬪瓙銆?nbsp; 闃呰鍏ㄦ枃
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闃呰鍏ㄦ枃
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鍏堢湅榪欎釜渚嬪瓙
bool Sales_item::same_isbn(const Sales_item &rhs) const
{ return (isbn rhs.isbn);}
钃濊壊鐨?span lang=EN-US>const鐢ㄤ簬淇グ鏄劇ず浼犲叆鐨勫艦鍙?span lang=EN-US>rhs
錛岃屽浜庣被鐨勬垚鍛樺垯鏈夐殣寮忕殑錛岃屽鐨?span lang=EN-US>this鎸囬拡浣滀負褰㈠弬浼犲叆錛岃岀孩鑹查儴鍒嗙殑const姝ｆ槸淇グ榪欓儴鍒嗗弬鏁?span lang=EN-US>this錛?span lang=EN-US>const 鎴愬憳鍑芥暟鐨勫紩鍏?span lang=EN-US>
鐜板湪錛屽彲浠ョ悊瑙ｈ窡鍦?span lang=EN-US>Sales_item 鎴愬憳鍑芥暟澹版槑鐨勫艦鍙傝〃鍚庨潰鐨?span lang=EN-US>const 鎵璧風殑浣滅敤浜?span lang=EN-US>: const鏀瑰彉浜嗛殣鍚殑this 褰㈠弬鐨勭被鍨嬨傚湪璋冪敤total.same_isbn(trans) 鏃訛紝闅愬惈鐨?span lang=EN-US>this 褰㈠弬灝嗘槸涓涓寚鍚?span lang=EN-US>total 瀵硅薄鐨?span lang=EN-US>const Sales_item*綾誨瀷鐨勬寚閽堛傚氨鍍忓涓嬬紪鍐?span lang=EN-US>same_isbn 鐨勫嚱鏁頒綋涓鏍?span lang=EN-US>:
/ / pseudo-code illustration of how the implicit this pointer is used/ / This code is illegal: We may not explicitly define the this pointer ourselves/ / Note that this is a pointer to const because same_isbn is a const memberbool Sales_item::same_isbn(const Sales item *const this ,const Sales_item &rhs) const
{ return (this->isbn rhs.isbn);}
鐢ㄨ繖縐嶆柟寮忎嬌鐢?span lang=EN-US>const 鐨勫嚱鏁扮О涓哄父閲忔垚鍛樺嚱鏁?span lang=EN-US>(const member function) 銆傜敱浜?span lang=EN-US>this 鏄寚鍚?span lang=EN-US>const 瀵硅薄鐨勬寚閽堬紝const 鎴愬憳鍑芥暟涓嶈兘淇敼璋冪敤璇ュ嚱鏁扮殑瀵硅薄銆傚洜姝わ紝鍑芥暟avg-price
鍜屽嚱鏁?span lang=EN-US>sarne isbn 鍙兘璇誨彇鑰屼笉鑳戒慨鏀硅皟鐢ㄥ畠浠殑瀵硅薄鐨勬暟鎹垚鍛樸?span lang=EN-US>
NOTE錛?span lang=EN-US>
const瀵硅薄鎸囧悜const鐨勬寚閽堟垨寮曠敤鍙兘鐢ㄤ簬璋冪敤鍏?span lang=EN-US>const鎴愬憳鍑芥暟濡傛灉灝濊瘯鐢ㄥ畠浠潵璋冪敤闈?span lang=EN-US>const 鎴愬憳鍑芥暟錛屽垯鏄敊璇殑銆?span lang=EN-US>
榪斿洖甯擱噺寮曠敤:
鍦ㄧ湅涓涓緥瀛愶細
1mycls const& returntest()//瀹氫箟榪斿洖鍊間負涓涓父閲忓紩鐢?/span>
2{
3
mycls my1(3);
4 cout<<"a in the func is"<<&my1<<endl;
5 return my1;
6
}
7int _tmain(int argc, _TCHAR* argv[])
8{
9 //嫻嬭瘯榪斿洖寮曠敤綾誨瀷
10 mycls const&str = returntest();//浣跨敤cont&鎺ュ彈榪斿洖鍊?br>11 //str.m_q=12;//緙栬瘧鎶ラ敊錛屼笉鍙互淇敼const綾誨瀷
12 mycls &str1=const_cast<mycls&>(str);//鍘繪帀const灞炴э紝浠ヤ究淇敼
13 str1.m_q=12;
14 cout<<"&b="<<&str<<endl;
15 cout<<"&b="<<&str1<<endl;
16 system("pause");
17 return 0;
18}
mycls const& returntest()//瀹氫箟榪斿洖鍊間負涓涓父閲忓紩鐢?/span>2
{3
mycls my1(3);4
cout<<"a in the func is"<<&my1<<endl;5
return my1;6
}7
int _tmain(int argc, _TCHAR* argv[])8
{9
//嫻嬭瘯榪斿洖寮曠敤綾誨瀷10
mycls const&str = returntest();//浣跨敤cont&鎺ュ彈榪斿洖鍊?br>11 //str.m_q=12;//緙栬瘧鎶ラ敊錛屼笉鍙互淇敼const綾誨瀷12
mycls &str1=const_cast<mycls&>(str);//鍘繪帀const灞炴э紝浠ヤ究淇敼13
str1.m_q=12;14
cout<<"&b="<<&str<<endl;15
cout<<"&b="<<&str1<<endl;16
system("pause");17
return 0; 18
}浠ヤ笂mycls鏄垜鑷繁瀹氫箟鐨勪竴涓被錛屽０鏄庡涓?br>
1class mycls
2{
3 public:
4 mycls(int a);
5 char a[100000];
6 //~mycls(void);
7 int m_q;
8 template <class T> inline int compare(const T &a,const T &b)
9
{
10 if(a == b)
11 return 0;
12 else if(a > b)
13 return 1;
14 else if(a<b)
15 return -1;
16 return 0;
17
}
18 mycls& operator+(mycls a);
19 virtual int dosomething(int a);
20 virtual void doanotherthing(void);
21};
22
閫氳繃浠ｇ爜娉ㄩ噴錛屾垜鎯寵繖涓嶉毦鐞嗚В錛岀敤涓涓紩鐢ㄧ被鍨嬬殑榪斿洖鍊兼渶澶уソ澶勫氨鏄彲浠ラ伩鍏嶅唴瀛樻嫹璐濓紝娉ㄦ剰鍒版垜鐨勭被涓湁涓涓暱搴︿負100000鐨刢har鏁扮粍錛屾垜鎯抽綣佹嫹璐濊繖涓暟緇勫浜庝竴涓嬫ц兘杈冧綆鐨勬満鍣ㄨ繕鏄緢鑰楁椂鐨勶紝榪欐椂鎴戜滑榪斿洖const &綾誨瀷錛岄伩鍏嶄簡鏂囦歡鐨勬嫹璐濓紝浠庤緭鍑轟篃鍙互鐪嬪埌錛宺eturntest鍑芥暟鍐呯殑瀵硅薄鍦板潃涓巑ain鍑芥暟鍐呮墍榪斿洖鐨勫紩鐢ㄥ璞″湴鍧瀹屽叏涓鑷淬?/span>
class mycls2
{3
public:4
mycls(int a);5
char a[100000];6
//~mycls(void);7
int m_q;8
template <class T> inline int compare(const T &a,const T &b)9
{10
if(a == b)11
return 0;12
else if(a > b)13
return 1;14
else if(a<b)15
return -1;16
return 0;17
}18
mycls& operator+(mycls a);19
virtual int dosomething(int a);20
virtual void doanotherthing(void);21
};22
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1#include <map>
2#include <iostream>
3#include <sstream>
4#include <fstream>
5#include <string>
6#include <stdexcept>
7using namespace std;
8int
9main(int args,char* argv[])
10{
11 try
12 {
13 if(args<3)
14 throw runtime_error("緙哄皯鍙傛暟錛岃杈撳叆銆傘傘?/span>");
15 ifstream fin;
16 fin.open(argv[1]);
17 if(!fin) //媯鏌ユ枃浠舵槸鍚﹁姝ｇ‘鎵撳紑
18 throw runtime_error("map file not found");
19 string keystr,mapstr;
20 map<string,string> mappedctner;
21 while(fin>>keystr>>mapstr)
22 {
23 mappedctner[keystr]=mapstr;//閲囩敤涓嬫爣寮曠敤鐨勬柟娉曟彃鍏ュ厓绱?br>24 }
25 for(int cnt(2);cnt!=args;cnt++)
26 {
27 fin.close();
28 fin.clear();
29 fin.open(argv[cnt]);
30 stringstream sstr;
31 sstr<<"target file "<<cnt-1<<" not found"<<endl;//鏍煎紡鍖栧瓧涓?br>32 if(!fin)
33 throw runtime_error(sstr.str());//str()鎴愬憳瀛樺偍杈撳叆鐨勬枃鏈璞?br>34 map<string,string>::iterator itr;
35 while(fin>>keystr)
36 {
37 if((itr=mappedctner.find(keystr))!=mappedctner.end())
38 keystr=itr->second;//鎵懼埌鐩稿叧瀛椾覆錛屽埄鐢ㄨ凱浠ｅ櫒寮曠敤second鐨刴appedvalue綾誨瀷鏇挎崲
39 cout<<keystr<<" ";
40 }
41 cout<<endl;
42 }
43 }
44 catch(runtime_error e)
45 {
46 cout<<e.what()<<endl;
47 }
48 catch(ios_base::failure e)
49 {
50 cout<<e.what()<<endl;
51 }
52 return 0;
53}
54
#include <map>2
#include <iostream>3
#include <sstream>4
#include <fstream>5
#include <string>6
#include <stdexcept>7
using namespace std;8
int9
main(int args,char* argv[])10
{11
try12
{13
if(args<3)14
throw runtime_error("緙哄皯鍙傛暟錛岃杈撳叆銆傘傘?/span>");15
ifstream fin;16
fin.open(argv[1]);17
if(!fin) //媯鏌ユ枃浠舵槸鍚﹁姝ｇ‘鎵撳紑18
throw runtime_error("map file not found");19
string keystr,mapstr;20
map<string,string> mappedctner;21
while(fin>>keystr>>mapstr)22
{23
mappedctner[keystr]=mapstr;//閲囩敤涓嬫爣寮曠敤鐨勬柟娉曟彃鍏ュ厓绱?br>24 }25
for(int cnt(2);cnt!=args;cnt++)26
{27
fin.close();28
fin.clear();29
fin.open(argv[cnt]);30
stringstream sstr;31
sstr<<"target file "<<cnt-1<<" not found"<<endl;//鏍煎紡鍖栧瓧涓?br>32 if(!fin)33
throw runtime_error(sstr.str());//str()鎴愬憳瀛樺偍杈撳叆鐨勬枃鏈璞?br>34 map<string,string>::iterator itr;35
while(fin>>keystr)36
{37
if((itr=mappedctner.find(keystr))!=mappedctner.end())38
keystr=itr->second;//鎵懼埌鐩稿叧瀛椾覆錛屽埄鐢ㄨ凱浠ｅ櫒寮曠敤second鐨刴appedvalue綾誨瀷鏇挎崲39
cout<<keystr<<" ";40
}41
cout<<endl;42
}43
}44
catch(runtime_error e)45
{46
cout<<e.what()<<endl;47
}48
catch(ios_base::failure e)49
{50
cout<<e.what()<<endl; 51
}52
return 0;53
}54
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