C++——指针3

指针作为函数参量

指针作为函数参量，以地址的方式传递数据，可以用来返回函数处理结果；实参是数组名时形参可以是指针。

题目：读入三个浮点数，将整数部分和小数部分分别输出

#include <iostream>

using namespace std;

void splitfloat(float x, int *intpart, float *fracpart)

{ //形参intpart、 fracpart是指针

*intpart=int(x); // 取x的整数部分

*fracpart=x-*intpart; //取x的小数部分

}

int main()

{

int i, n;

float x, f;

cout<<"Enter three(3) floating point numbers"
<< endl;

for (i = 0; i < 3; i++)

{

cin >> x;

splitfloat(x,&n,&f); //变量地址做实参

cout<<"Integer Part is "<< n
<<" Fraction Part is "<<f<<endl;

}

运行结果：

Enter three(3) floating point numbers

4.7

Integer Part is 4 Fraction Part is 0.7

8.913

Integer Part is 8 Fraction Part is 0.913

-4.7518

Integer Part is -4 Fraction Part is -0.7518

输出数组元素的内容和地址

#include <iostream>

#include <iomanip>

using namespace std;

void Array_Ptr(long *P, int n)

{ int i;

cout<<"In func, address of array is "
<<unsigned long(P)<<endl;

cout<<"Accessing array using pointers"<< endl;

for (i = 0; i < n; i++)

{ cout<<" Address for index "<<i<<" is "
<<unsigned long(P+i);

cout<<" Value is "<<*(P+i)<<endl;

}

int main()

{ long list[5]={50, 60, 70, 80, 90};

cout<<"In main, address of array is "

<< unsigned long(list)<<endl;

cout<<endl;

Array_Ptr(list,5);

}

某一次运行结果：

In main, address of array is 6684132

In func, address of array is 6684132

Accessing array using pointers

Address for index 0 is 6684132 Value is 50

Address for index 1 is 6684136 Value is 60

Address for index 2 is 6684140 Value is 70

Address for index 3 is 6684144 Value is 80

Address for index 4 is 6684148 Value is 90

用指向常量的指针做形参

#include<iostream>

using namespace std;

const int N=6;

void print(const int *p,int n);

int main()

{ int array[N];

for(int i=0;i<N;i++)

cin>>array[i];

print(array,N);

}

void print(const int *p, int n)

{

cout<<"{"<<*p;

for(int i=1;i<n;i++)

cout<<"."<<*(p+i);

cout<<"}"<<endl;

}

当函数的返回值是地址时，该函数就是指针型函数。声明：存储类型 数据类型 *函数名（）；

指向函数的指针 存储类型 数据类型 （*函数名）（）；数据指针指向数据存储区，而函数指针指向的程序代码的存储区（函数名是函数代码的恰是地址）。

#include <iostream>

using namespace std;

void print_stuff(float data_to_ignore);

void print_message(float list_this_data);

void print_float(float data_to_print);

void (*function_pointer)(float); //void类型的函数指针

int main() //主函数

{

float pi = (float)3.14159;

float two_pi = (float)2.0 * pi;

print_stuff(pi);

function_pointer = print_stuff; //函数指针指向print_stuff

function_pointer(pi); //函数指针调用,相当于调用print_stuff

function_pointer = print_message; //函数指针指向print_message

function_pointer(two_pi); //函数指针调用

function_pointer(13.0); //函数指针调用

function_pointer = print_float; //函数指针指向print_float

function_pointer(pi); //函数指针调用

print_float(pi);

}

void print_stuff(float data_to_ignore)

{ cout<<"This is the print stuff function.\n"; }

void print_message(float list_this_data)

{ cout<<"The data to be listed is "<<list_this_data<<endl; }

void print_float(float data_to_print)

{ cout<<"The data to be printed is "<<data_to_print<<endl; }

//运行结果：

This is the print stuff function.

The data to be listed is 6.283180

The data to be listed is 13.000000

The data to be printed is 3.141590

巴特西

C++——指针3

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