温州外贸网站推广,邢台如何做企业网站,正规轻电商网站模板,网站建设服务商有哪些9.1 单独编译 Visual Studio中新建头文件和源代码
通过解决方案资源管理器#xff0c;如图所示#xff1a; 分成三部分的程序#xff08;直角坐标转换为极坐标#xff09;
头文件coordin.h
#ifndef __COORDIN_H__ // 如果没有被定义过
#define __COORDIN_H__struct pola…9.1 单独编译 Visual Studio中新建头文件和源代码
通过解决方案资源管理器如图所示 分成三部分的程序直角坐标转换为极坐标
头文件coordin.h
#ifndef __COORDIN_H__ // 如果没有被定义过
#define __COORDIN_H__struct polar {double distance;double angle;
};struct rect {double x;double y;
};polar rect_to_polar(rect xypos);
void show_polar(polar dapos);#endif // 如果被定义过了啥也不做
源代码file1放置main函数调用其他函数
#include iostream
#include coordin.h // 尖括号表明去系统目录找双引号表明去当前目录找
using namespace std;int main(){rect rplace;polar pplace;cout Enter the x and y values: ;while (cin rplace.x rplace.y) {pplace rect_to_polar(rplace);show_polar(pplace);cout Next two numbers (q to quit): ;}cout Bye! endl;return 0;
}源代码file2其他函数的定义
#include iostream
#include cmath
#include coordin.hpolar rect_to_polar(rect xypos) {using namespace std;polar answer;answer.distance sqrt(xypos.x * xypos.x xypos.y * xypos.y);answer.angle atan2(xypos.y, xypos.x);return answer;
}void show_polar(polar dapos) {using namespace std;const double Rad_to_deg 57.29577951;cout distance dapos.distance;cout , angle dapos.angle * Rad_to_deg;cout degrees endl;
}
9.2 存储持续性、作用域和链接性 全局变量和局部变量
头文件support.h
#ifndef __SUPPORT_H__
#define __SUPPORT_H__
#include iostreamextern double warming; // 声明外部变量(不要赋值)void update(double dt);
void local(void);#endif
源代码external.cpp
#include iostream
#include support.h
using namespace std;double warming 0.3;int main(){cout Global warming is warming endl;update(0.1);cout Global warming is warming endl;local();return 0;
}源代码support.cpp
#include support.h
using namespace std;void update(double dt) {warming dt;cout Updating global warming to warming endl;
}void local(void) {double warming 0.8; // 局部变量只在local内部可见cout Local warming is warming endl;// 作用域解析运算符(::),放在变量名前表示使用变量的全局版本cout But global warming is ::warming endl;
}
static限定符用于全局变量
源代码twofile1.cpp
#include iostream
using namespace std;int tom 3;
int dick 30;
static int harry 300; // 仅在twofile1.cpp可见
void remote_access(void);int main() {cout main() reports the following addresses: endl;cout tom tom endl;cout dick dick endl;cout harry harry endl;remote_access();return 0;
}
源代码twofile2.cpp
#include iostream
using namespace std;extern int tom; // 声明为外部变量(来自twofile1.cpp)
static int dick 10; // 只在twofile2.cpp中可见
int harry 200; // 新建一个全局变量void remote_access(void) {cout remote_access() reports the following addresses: endl;cout tom tom endl;cout dick dick endl;cout harry harry endl;
}
static限定符用于局部变量统计字符串的字符个数
#include iostream
using namespace std;const int ArSize 10;
void strcount(const char * str);int main(){char input[ArSize];char next;cout Enter a line: endl;cin.get(input, ArSize);while (cin) {cin.get(next);// 如果输入的内容大于10个字符则用cin.get全部消耗掉while (next ! \n)cin.get(next);strcount(input);cout Enter next line (empty line to quit): endl;cin.get(input, ArSize);}cout Bye! endl;return 0;
}void strcount(const char * str) {// 局部变量加static无论调用多少次这个函数该变量只会在第一次初始化static int total 0;int count 0;while (*str) {count;str;}total count;cout count characters. endl;cout total characters total. endl;
}定位new运算符的使用
#include iostream
#include new
using namespace std;const int BUF 512;
const int N 5;
char buffer[BUF];int main(){double *pd1, *pd2;int i;cout Calling new and placement new: endl;// 用常规new运算符为N个double类型开辟内存空间pd1 new double[N];// 用定位new运算符为N个double类型开辟内存空间pd2 new (buffer) double[N];// 赋值for (int i 0; i N; i) {pd2[i] pd1[i] 1000 20.0 * i;}cout pd1 pd1 , buffer (void *)buffer endl;// 打印pd1和pd2的地址for (int i 0; i N; i) {cout pd1[i] at pd1[i] ;;cout pd2[i] at pd2[i] endl;}cout \nCalling new and placement new a second time: endl;double *pd3, *pd4;pd3 new double[N];pd4 new(buffer) double[N]; // 会覆盖掉原来地址里的值for (int i 0; i N; i) {pd4[i] pd3[i] 1000 40.0 * i;}for (int i 0; i N; i) {cout pd3[i] at pd3[i] ;;cout pd4[i] at pd4[i] endl;}cout \nCalling new and placement new a third time: endl;delete[] pd1;pd1 new double[N]; // 删了重新new(申请和之前相同的地方)pd2 new(buffer N * sizeof(double)) double[N]; // 地址往后偏移5个double类型的长度for (int i 0; i N; i) {pd2[i] pd1[i] 1000 60.0 * i;}for (int i 0; i N; i) {cout pd1[i] at pd1[i] ;;cout pd2[i] at pd2[i] endl;}delete[] pd1;delete[] pd3; // pd2和pd4是定位new开辟出来的delete不能用于定位newreturn 0;
}
9.3 名称空间 当名称空间和声明区域定义了相同名称伪代码
namespace Jill{double bucket(double n) {...}double fetch;struct Hill {...};
}
char fetch; // 全局变量
int main(){using namespace Jill; // 使用using编译指令Hill Thrill; // 创建一个Jill::Hill 的结构double water bucket(2); // 使用Jill::bucket()double fetch; // 不会出错Jill::fetch被隐藏cin fetch; // 读入一个数据到局部变量fetchcin ::fetch; // 读入一个数据到全局变量fetchcin Jill::fetch; // 读入一个变量到Jill::fetch...
}int foom(){Hill top; // 会出错Jill::Hill crest; // 可用
}
名称空间示例打印人名及欠款
头文件namesp.h
#pragma once
#include stringnamespace pers {struct Person {std::string fname;std::string lname;};void getPerson(Person rp);void showPerson(const Person rp);
}namespace debts {using namespace pers;struct Debt {Person name;double amount;};void getDebt(Debt rd);void showDebt(const Debt rd);double sunDebts(const Debt ar[], int n);
}
源代码namessp.cpp
#include iostream
#include namesp.hint main() {using debts::Debt;using debts::showDebt;Debt golf { {Micheal, Jordan}, 120.0 };showDebt(golf);return 0;
}
源代码namesp.cpp
#include iostream
#include namesp.h // 头文件放结构体类型、函数原型声明namespace pers {using std::cout;using std::cin;void getPerson(Person rp) {cout Enter first name: ;cin rp.fname;cout Enter last name: ;cin rp.lname;}void showPerson(const Person rp) {cout rp.lname , rp.fname;}
}namespace debts {void getDebt(Debt rd) {getPerson(rd.name);std::cout Enter debt: ;std::cin rd.amount;}void showDebt(const Debt rd) {showPerson(rd.name);std::cout : $ rd.amount std::endl;}double sunDebts(const Debt ar[], int n) {double total 0;for (int i 0; i n; i) {total ar[i].amount;}return total;}
}
