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◆数组和字符串
从表面上看，一个字符串就是一个字符数组，但在C++语句中，两者并不完全相同。
字符串是一个以串尾符"\0"结尾的字符型数组，但任一个字符型数组不见得必为字符串(因为其中可以不包含"\0"结尾字符)。
 char string1[7]="China";
char string2[]="China";
  char string3[7]={'C','h','i','n','a'};
char string4[7]={'C','h','i','n','a','\0'};
string1的长度为7，赋初值后其前6个元素已被赋值(第6个元素为'\0')； string2的长度为6(第6个元素为'\0')； string3的长度为7，最后没有串尾符'\0'； string4的长度为7，赋初值后与string1相同。 ◆字符指针与其他类型指针的使用区别 读下列程序：
1#include<iostream>
2using namespace std;
3int main()
4{
5 char str[10]="abcdefghi";
6  int a[10]={0,1,2,3,4,5,6,7,8,9};
7 cout<<"'cout<<str'=>"<<str<<endl;
8 cout<<"'cout<<a'=>"<<a<<endl;
9 cout<<"--------------------"<<endl;
10 cout<<"'cout<<&str'=>"<<&str<<endl;
11 cout<<"'cout<<&a'=>"<<&a<<endl;
12 cout<<"--------------------"<<endl;
13 cout<<"'cout<<(int*)str'=>"<<(int*)str<<endl;
14 cout<<"'cout<<(double*)a'=>"<<(double*)a<<endl;
15 cout<<"--------------------"<<endl;
16 cout<<"'cout<<str+1'=>"<<str+1<<endl;
17 cout<<"'cout<<a+1'=>"<<a+1<<endl;
18 cout<<"--------------------"<<endl;
19 cout<<"'cout<<&str[1]'=>"<<&str[1]<<endl;
20 cout<<"'cout<<&a[1]'=>"<<&a[1]<<endl;
21 cout<<"--------------------"<<endl;
22 cout<<"'cout<<(int*)(str+1)'=>"<<(int*)(str+1)<<endl;
23 cout<<"'cout<<(double*)(a+1)'=>"<<(double*)(a+1)<<endl;
24 cout<<"--------------------"<<endl;
25 cout<<"'cout<<(double*)(&str[1])'=>"<<(double*)(&str[1])<<endl;
26 cout<<"'cout<<(double*)(&a[1])'=>"<<(double*)(&a[1])<<endl;
27 cout<<"--------------------"<<endl;
28 return 0;
29 }
30
输出结果：
1'cout<<str'=>abcdefghi
2'cout<<a'=>0X0065FDC4 //存放地址，可以不同(下同)
3--------------------------
4'cout<<&str'=>0X0065FDEC
5'cout<<&a'=>0X0065FDC4
6--------------------------
7'cout<<(int*)str'=>0X0065FDEC
8'cout<<(double*)a'=>0X0065FDC4
9--------------------------
10'cout<<str+1'=>bcdefghi
11'cout<<a+1'=>0X0065FDC8
12--------------------------
13'cout<<&str[1]'=>bcdefghi
14'cout<<&a[1]'=>0X0065FDC8
15--------------------------
16'cout<<(int*)(str+1)'=>0X0065FDED
17'cout<<(double*)(a+1)'=>0X0065FDC8
18--------------------------
19'cout<<(double*)(&str[1])'=>0X0065FDED
20'cout<<(double*)(&a[1])'=>0X0065FDC8
21--------------------------
分析： 字符指针与其他类型的指针(如int型指针)在使用上是有所区别的(字符指针具有其特殊性)。如，输出字符数组名即字符指针 ，就是输出字符指针所指向的那一个字符串；而输出int型数组名即int型指针，就是输出当前的指针值(一个地址)。但输出 字符数组名取地址，或输出int型数组名取地址，都可以输出当前的指针值(一个地址)。另外，若将字符数组名即字符指针 的类型进行转换后，输出的将是当前的指针值(一个地址)。 ◆赋值参数、指针参数以及引用参数的使用区别 读下面程序：
1#include<iostream>
2using namespace std;
3int myFunc(int i1,int* pi21,int*& pi22,int& ri3,char* str);
4
5int main()
6{
7 int i=1,a[2]={21,202},*pa=a,b[2]={21,202},*pb=b,r=3456;
8 char s[]="ABCDEFG";
9 cout<<"--------In main position 1--------"<<endl;
10 cout<<"i,*pa,*pb,r,s="<<i<<","<<*pa<<","<<*pb<<","
11 <<r<<","<<s<<endl;
12 cout<<"a[0],a[1],b[0],b[1]="<<a[0]<<","<<a[1]<<","
13 <<b[0]<<","<<b[1]<<endl;
14 int tmp=myFunc(i,pa,pb,r,s);
15 cout<<"--------In main position2 2--------"<<endl;
16 cout<<"i,*pa,*pb,r,s="<<i<<","<<*pa<<","<<*pb<<","
17 <<r<<","<<s<<endl;
18 cout<<"a[0],a[1],b[0],b[1]="<<a[0]<<","<<a[1]<<","
19 <<b[0]<<","<<b[1]<<endl;
20 cout<<"tmp="<<tmp<<endl;
21 return 0;
22}
23int myFunc(int i1,int* pi21,int*& pi22,int& ri3,char* str)
24{
25 cout<<"--------In myFunc position 1-------"<<endl;
26 cout<<"i1,*pi21,*pi22,ri3,str="<<i1<<","<<*pi21<<","
27 <<*pi22<<","<<ri3<<","<<str<<endl;
28 i1++;
29 pi21++;
30 pi22++;
31 ri3++;
32 (*str)++;
33 cout<<"--------In myFunc position 2-------"<<endl;
34 cout<<"i1,*pi21,*pi22,ri3,str="<<i1<<","<<*pi21<<","
35 <<*pi22<<","<<ri3<<","<<str<<endl;
36 i1++;
37 (*pi21)++;
38 (*pi22)++;
39 ri3++;
40 str++;
41 cout<<"--------In myFunc position 3-------"<<endl;
42 cout<<"i1,*pi21,*pi22,ri3,str="<<i1<<","<<*pi21<<","
43 <<*pi22<<","<<ri3<<","<<str<<endl;
44
45 return i1;
46}
47
运行结果为：
--------In main position 1--------
i,*pa,*pb,r,s=1,21,21,3456,ABCDEFG
a[0],a[1],b[0],b[1]=21,202,21,202
--------In myFunc position 1-------
i1,*pi21,*pi22,ri3,str=1,21,21,3456,ABCDEFG
--------In myFunc position 2-------
i1,*pi21,*pi22,ri3,str=2,202,202,3457,BBCDEFG
--------In myFunc position 3-------
i1,*pi21,*pi22,ri3,str=3,203,203,3458,BCDEFG
--------In main position2 2--------
i,*pa,*pb,r,s=1,21,203,3458,BBCDEFG
a[0],a[1],b[0],b[1]=21,203,21,203
tmp=3
◆函数指针 读程序：
1#include<iostream>
2#include<cmath>
3using namespace std;
4double func1(double x);
5double func2(double y);
6double func3(double z);
7void processing(double x,double(*fpt)(double));
8
9int main()
10{
11 double x,res;
12 double (*fp)(double);
13 cout<<"Input a real number:";
14 cin>>x;
15 fp=func1;
16 res=(*fp)(x);
17 cout<<"res=(*fp)(x)="<<res<<endl;
18 fp=func2;
19 res=(*fp)(x);
20 cout<<"res=(*fp)(x)="<<res<<endl;
21 processing(x,func3);
22 fp=func3;
23 processing(x,fp);
24 return 0;
25}
26double func1(double x)
27{
28 cout<<" ---Call func1: 1/x="<<1/x<<endl;
29 return (1/x);
30}
31double func2(double x)
32{
33 cout<<" ---Call func2: x*x="<<x*x<<endl;
34 return (x*x);
35}
36double func3(double x)
37{
38 cout<<" ---Call func3: sqrt(x)="<<sqrt(x)<<endl;
39 return sqrt(x);
40}
41void processing(double x,double (*fpt)(double))
42{
43 cout<<" ---Call processing"<<endl;
44 double result=(*fpt)(x);
45 cout<<" ---result=(*fpt)(x)="<<result<<endl;
46}
47
结果显示：
Input a real number:5.5
---Call func1: 1/x=0.181818
res=(*fp)(x)=0.181818
---Call func2: x*x=30.25
res=(*fp)(x)=30.25
---Call processing
---Call func3: sqrt(x)=2.34512
---result=(*fpt)(x)=2.34512
---Call processing
---Call func3: sqrt(x)=2.34512
---result=(*fpt)(x)=2.34512
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