所有子任务的函数(例子代码)

第四章

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今晚敲代码真是分心了，敲错N次变量名，估计是边看电影便做事的缘故。

//4.2void函数 //这个程序将华氏温度换算为摄氏温度 #include<iostream> #include<stdlib.h> void initialize_screen(); //将当前输出与上一个程序的输出分开 double celsius(double fahrenheit); //将华氏温度换算为温度 void show_results(double f_degrees,double c_degrees); //显示输出，假定摄氏温度c_degrees等价于华氏温度f_degrees int main() { using namespace std; double f_temperature,c_temperature; initialize_screen(); cout<<"I will convert a Fahrenheit temperture to Celsius./n" <<"Enter a temprature in Fahrenheit: "; cin>>f_temperature; c_temperature=celsius(f_temperature); show_results(f_temperature,c_temperature); system("pause"); return 0; } //函数定义使用了iostream void initialize_screen() { using namespace std; cout<<endl; return; //这个return语句是可选的 } double celsius(double fahrenheit) { return((5.0/9.0)*(fahrenheit-32)); } //函数定义使用了iostream void show_results(double f_degrees,double c_degrees) { using namespace std; cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(1); cout<<f_degrees <<" degrees Fahrenheit is wquivalent to/n" <<c_degrees<<" degress Celsius./n"; return;//这个return语句是可选的 }

2010.12.11

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//在void函数中使用return语句 //代码片段解析 //函数声明 void ice_cream_division(int number,double total_weight); //针对为number位客户分配总重量为total_weight盎司的冰欺凌，输出相应的指示 //如果number等于0，则什么都不做 //函数定义 //函数使用了iostream: void ice_cream_division(int number,double total_weight) { using namespace std; double portion; if(number==0) { return;//如果number等于0，执行终止 } portion=total_weight/number; cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); cout<<"Each on receives " <<portion<<" ounces of ice cream."<<endl; }

(add in 2010.12.15)

//4.4传引用调用参数 //演示传引用调用参数的程序 #include<iostream> #include<stdlib.h> void get_numbers(int& input1,int& input2); //从键盘读取两个整数 void swap_values(int& variable1,int& variable2); //交换variable1和variable2的值 void show_results(int output1,int output2); //依次显示variable1和variable2的值 int main() { int first_num,second_num; get_numbers(first_num,second_num); swap_values(first_num,second_num); show_results(first_num,second_num); system("pause"); return 0; } //使用iostream void get_numbers(int& input1,int& input2) { using namespace std; cout<<"Enter two integers: "; cin >>input1 >>input2; } void swap_values(int& variable1,int& variable2) { int temp; temp=variable1; variable1=variable2; variable2=temp; } //使用iostream void show_results(int output1,int output2) { using namespace std; cout<<"In reverse order the numbers are: " <<output1<<" "<<output2<<endl; }

——2010.12.12

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//4.6比较两种参数传递机制 //展示传值调用参数和传引用调用参数的区别 #include<iostream> #include<cstdlib> void do_stuff(int par1_value,int& par2_ref); //par1_value是传值调用参数,par2_ref是传引用调用参数 int main() { using namespace std; int n1,n2; n1=1; n2=2; do_stuff(n1,n2); cout<<"n1 after function call= "<<n1<<endl; cout<<"n2 after function call= "<<n2<<endl; system("pause"); return 0; } void do_stuff(int par1_value,int& par2_ref) { using namespace std; par1_value=111; cout<<"par1_value in function call= " <<par1_value<<endl; par2_ref=2; cout<<"par2_value in function call= " <<par2_ref<<endl; }

——2010.12.14

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 //4.7疏忽的局部变量 //演示引用调用参数的程序 #include<iostream> #include<cstdlib> void get_numbers(int& input1,int& input2); //从键盘读取两个整数 void swap_values(int variable1,int variable2);//此处int后忘记加& //交换variable1和variable2的值 void show_results(int output1,int output2); //依次输出variable1和variable2的值 int main() { using namespace std; int first_num,second_num; get_numbers(first_num,second_num); swap_values(first_num,second_num); show_results(first_num,second_num); system("pause"); return 0; } //使用iostream: void get_numbers(int& input1,int& input2) { using namespace std; cout<<"Enter two integers: "; cin>>input1 >>input2; } void swap_values(int variable1,int variable2) //此处int后忘记加& { int temp; temp=variable1; variable1=variable2; variable2=temp; // variable1, variable2 ：疏忽的局部变量 } //使用iostream: void show_results(int output1,int output2) { using namespace std; cout<<"In reverse order the numbers are: " <<output1<<" "<<output2<<endl; }

——2010.12.15

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//4.8一个函数调用另一个函数 //该程序用于演示一个函数调用另一个函数 #include<iostream> #include<cstdlib> void get_input(int& input1,int& input2); //从键盘读取两个整数 void swap_values(int& variable1,int& variable2); //交换 variable1和variable2的值 void order(int& n1,int& n2); //对n1和n2变量中的数字进行排序。函数调用之后，n1<=n2. void give_results(int output1,int output2); //输出output1和output2中的值 //假定output1<=output2 int main() { int first_num,second_num; get_input(first_num,second_num); order(first_num,second_num); give_results(first_num,second_num); system("pause"); return 0; } //使用iostream: void get_input(int& input1,int& input2) { using namespace std; cout<<"Enter two integers: "; cin>>input1 >>input2; } void swap_values(int& variable1,int& variable2) { int temp; temp=variable1; variable1=variable2; variable2=temp; } void order(int& n1,int& n2) { if(n1>n2) { swap_values(n1,n2); //函数调用 } } //使用iosream: void give_results(int output1,int output2) { using namespace std; cout<<"In incteasing order the numbers are: " <<output1<<" "<<output2<<endl; }

——2010.12.16

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//4.9超市定价系统 //根据Quick-Shop连锁超市的定价策略来确定一件商品的零售价 #include<iostream> #include<cstdlib> const double LOW_MARKUP=0.05; //低涨幅5% const double HIGH_MARKUP=0.10; //高涨幅10% const int THRESHOLD=7; //如果预计7天内无法售出，则使用MARKUP void introduction(); //后条件：在屏幕上输出程序说明 void get_input(double& cost,int& turnover ); //前条件：用户准备好输入正确的值 //后条件：cost的值设为一件商品的批发价 //turnover的值设为商品预计出售的天数 double price(double cost,int turnover); //前条件：cost是一件商品的批发价 //turnover是商品预计售出的天数 //返回商品的零售价 void give_output(double cost,int turnover,double price); //前条件：cost是一件商品的批发价，turnover是商品 //预计售出的天数，price是商品的零售价 //侯条件：在屏幕上输出cost，turnover和price的值 int main() { double wholesale_cost,retail_price; int shelf_time; introduction(); get_input(wholesale_cost,shelf_time); retail_price=price(wholesale_cost,shelf_time); give_output(wholesale_cost,shelf_time,retail_price); system("pause"); return 0; } //使用iostream: void introduction() { using namespace std; cout<<"This program determines the retail price for/n" <<"an item at a Quick-Shop supermaket store./n"; } //使用iostream: void get_input(double& cost,int& turnover ) { using namespace std; cout<<"Enter the wholesale cost of item: $"; cin>>cost; cout<<"Enter the expected number of days until sold: "; cin>>turnover; } //使用iostream: void give_output(double cost,int turnover,double price) { using namespace std; cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); cout<<"Wholesale cost= $"<<cost<<endl <<"Expected time unitl sold = " <<turnover<<" days"<<endl <<"Retail price= $"<<price<<endl; } //使用已定义的常量LOW_MARKUP,HIGH_MARKUP和THRESHOLD: double price(double cost,int turnover) { if(turnover<=THRESHOLD) { return(cost+(LOW_MARKUP*cost)); } else { return(cost+(HIGH_MARKUP*cost)); } }

 

//4.10驱动程序 //get_input函数的驱动程序 #include<iostream> void get_input(double& cost,int& turnover); //前条件：用户准备好输入正确的值 //后条件：cost的值设为一件商品的批发价 //turnover的值设为商品预计售出的天数 int main() { using namespace std; double wholesale_cost; int shelf_time; char ans; cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); do { get_input(wholesale_cost,shelf_time); cout<<"Wholesale cost is now $" <<wholesale_cost<<endl; cout<<"Days until sold is now " <<shelf_time<<endl; cout<<"Test again?" <<" (Type Y for yes or N for no): "; cin>>ans; cout<<endl; }while(ans=='Y'||ans=='y'); return 0; } //使用iostream: void get_input(double& cost,int& turnover) { using namespace std; cout<<"Enter the wholesale cost of item: $"; cin>>cost; cout<<"Enter the expected number of days until sold: "; cin>>turnover; }

——2010.12.18

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//4.11含有stub的程序 //根据Quick-Shop连锁超市的定价策略来判断一件商品的零售价 #include<iostream> #include<cstdlib> void introduction(); //后条件：在屏幕上输出程序说明 void get_input(double& cost,int& turnover); //前条件：用户准备好输入正确的值 //后条件：cost的值设置为一件商品的批发价 //turnover设置为商品预计售出的天数 double price(double cost,int turnover); //前条件:cost是一件商品的批发价 //turnover是商品预计售出的天数 //返回商品的零售价 void give_output(double cost,int turnover,double price); //前条件：cost是一件商品的批发价 //turnover是商品预计售出的天数 //返回商品的零售价 int main() { double wholesale_cost,retail_price; int shelf_time; introduction(); get_input(wholesale_cost,shelf_time); retail_price=price(wholesale_cost,shelf_time); give_output(wholesale_cost,shelf_time,retail_price); system("pause"); return 0; } //使用iostream: 完全通过测试的函数 void introduction() { using namespace std; cout<<"This program determines the retail price for /n" <<"an item at a Quick-Shop supermarket store. /n"; } //使用iostream: 完全通过测试的函数 void get_input(double& cost,int& turnover) { using namespace std; cout<<"Enter the wholesale cost of item: $"; cin>>cost; cout<<"Enter the expected number of days until sold: "; cin>>turnover; } //使用iostream: 正在进行测试的函数 void give_output(double cost,int turnover,double price) { using namespace std; cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); cout<<"Wholesale cost= $"<<cost<<endl <<"Expected time until sold= " <<turnover<<" days"<<endl <<"Retail price= $"<<price<<endl; } //这只是一个stub: 测试函数 double price(double cost,int turnover) { return 9.99; //虽然不正确，但完全可用于测试 }

——2010.12.21

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This chapter is over!