过程抽象和返回一个值的函数(例子代码)

最新推荐文章于 2020-02-21 17:34:26 发布

转载最新推荐文章于 2020-02-21 17:34:26 发布 · 606 阅读

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本文通过多个示例展示了C++中的函数定义、调用、重载等编程技巧，包括计算狗舍大小、评估购物成本、成绩判断、比萨性价比等实际应用案例。

//3.1函数调用 //r根据用户的预算，计算可以购买多大的狗舍 // #include<iostream> #include<cmath> #include<stdlib.h> using namespace std; int main() { const double COST_PER_SQ_FT = 10.50; double budget,area,length_side; cout << "Enter the amout budgeted for your dog house $"; cin >> budget; area=budget/COST_PER_SQ_FT; length_side=sqrt(area); cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); cout<<"For a price of $"<<budget<<endl <<"I can build you a luxurious square dog house/n" <<"that is "<<length_side <<" feet on each sibe./n"; system("pause"); return 0; }

前些天一直不晓得cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); 是干什么用的，今天终于查到了：setf()是追加标志字的函数,而flags()是设置标志字；fixed标志是以定点形式显示浮点数；showpoint标志是强制显示小数点；precision就是精度，表示输出多少小数位。

——2010.12.4

// 3.3函数的定义 // #include<iostream> #include<stdlib.h> using namespace std; double total_cost(int number_par,double price_par); //函数声明，计算以单价price_par购买number_par件商品的总价，含5%税销售 int main() { double price,bill; int number; cout<<"Enter the number of items purchased: "; cin>>number; cout<<"Enter the price per item $"; cin>>price; bill=total_cost(number,price); //函数调用 cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); cout<<number<<" items at " <<"$"<<price<<" each./n" <<"Final bill,including tax,is $"<<bill <<endl; system("pause"); return 0; } double total_cost(int number_par,double price_par) { const double TAX_RATE=0.05;//5%税额 double subtotal; subtotal=price_par*number_par; return(subtotal+subtotal*TAX_RATE); }

——2010.12.5

//3.5实参顺序有错 //判断用户的成绩，要么为Pass(及格)，要么为Fail(不及格) #include<iostream> #include<stdlib.h> using namespace std; char grade(int received_par,int min_score_par); //如果received_par大于或等于min_score_par,返回'P'表示及格； //否则返回'F'表示不及格 int main() { int score,need_to_pass; char letter_grade; cout<<"Enter your score and the minimum needed to pass:/n"; cin>>score>>need_to_pass; letter_grade=grade(need_to_pass,score);//注意形参顺序 cout<<"You received a score of "<<score<<endl <<"Minimum to pass is "<<need_to_pass<<endl; if(letter_grade=='P') { cout<<"You passed. Congratulation!/n"; } else { cout<<"Sorry.You failed./n"; } cout<<letter_grade <<" will be entered in your record./n"; system("pause"); return 0; } char grade(int received_par,int min_score_par) { if(received_par>=min_score_par) { return 'P'; } else { return 'F'; } }

——2010.12.6

//3.9购买比萨
//判断两种比萨哪一种最适合购买
#include<iostream>
#include<stdlib.h>
using namespace std;

double unitprice(int diameter,double price);
//返回比萨每平方英寸的价格
//形参diameter是以英寸为单位的比萨直径，形参price是比萨的价格

int main()
{
	int diameter_small,diameter_large;
	double price_small,unitprice_small,
			price_large,unitprice_large;

cout<<"Welcome to the Pizza Consumers Union./n";
	cout<<"Enter diameter of a small pizza (in inches):";
	cin>>diameter_small;
	cout<<"Enter the price of a small pizz: $";
	cin>>price_small;
	cout<<"Enter diameter of a large pizza (in inches):";
	cin>>diameter_large;
	cout<<"Enter the price of a large pizz: $";
	cin>>price_large;

unitprice_small=unitprice(diameter_small,price_small);
	unitprice_large=unitprice(diameter_large,price_large);

cout.setf(ios::fixed);
	cout.setf(ios::showpoint);
	cout.precision(2);
	cout<<"Small pizza:/n"
		<<"Diameter= "<<diameter_small<<endl
		<<"Price= $"<<price_small
		<<" Per square inch= $"<<unitprice_small<<endl
		<<"Large pizza:/n"
		<<"Diameter= "<<diameter_large<<endl
		<<"Price= $"<<price_large
		<<" Per square inch= $"<<unitprice_large<<endl;

if(unitprice_large<unitprice_small)
	{
		cout<<"The large one is the better buy./n";
	}
	else
	{
		cout<<"The small one is the better buy./n";
	}
	cout<<"Buon Appetito!/n";

system("pause");
	return 0;
}

double unitprice(int diameter,double price)
{
	const double PI=3.14159;
	double radius,area;

radius=diameter/static_cast<double>(2); //强制类型转换保证结果精度和正确性
	area=PI*radius*radius;

return(price/area);
}

//3.10局部变量 //计算一块豌豆试验田的平均收成 #include<iostream> #include<stdlib.h> using namespace std; double est_total(int min_peas,int max_peas,int pod_count); //返回预计收获的豌豆总数 //形参pod_count是豆荚数 //形参min_peas和max_peas是每个豆荚中的最少和最多豌豆数 int main() { int max_count,min_count,pod_count; double average_pea,yield; //这里average_pea为main的局部变量 cout<<"Enter minimum and maximum number of peas in a pod: "; cin>>min_count>>max_count; cout<<"Enter the number of pods: "; cin>>pod_count; cout<<"Enter the weight of an average pea (in ounces): "; cin>>average_pea; yield=est_total(min_count,max_count,pod_count)*average_pea; cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); cout<<"Min number of peas per pod= "<<min_count<<endl <<"Max number of peas per pod= "<<max_count<<endl <<"Pod count = "<<pod_count<<endl <<"Average pea weight= " <<average_pea<<" ounces"<<endl <<"Estimated average yield= "<<yield<<" ounces"<<endl; system("pause"); return 0; } double est_total(int min_peas,int max_peas,int pod_count) { double average_pea; //这里average_pea为est_total的局部变量 average_pea=(max_peas+min_peas)/2.0; return(pod_count*average_pea); }

——2010.12.8

——2010.12.9

//3.13使用命名空间 //计算一个圆的面积和一个球体的体积 //两个计算使用相同的半径 #include<iostream> #include<stdlib.h> #include<cmath> const double PI=3.14159; double area(double radius); //返回具有指定半径的一个圆的面积 double volume(double radius); //返回具有指定半径的一个球的体积 int main() { using namespace std;//局部使用 double radius_of_both,area_of_circle,volume_of_sphere; cout<<"Enter a radius to use for both a circle and a sphere(in inches): /n"; cin>>radius_of_both; area_of_circle=area(radius_of_both); volume_of_sphere=volume(radius_of_both); cout<<"Radius= "<<radius_of_both<<" inches /n" <<"Area of circle= "<<area_of_circle<<" square inches/n" <<"Volume of sphere= "<<volume_of_sphere<<" cubic inches/n"; system("pause"); return 0; } double area(double radius) { using namespace std;//局部使用 return(PI*pow(radius,2)); } double volume(double radius) { using namespace std;//局部使用 return((4.0/3.0)*PI*pow(radius,3)); }

//3.15重载一个函数名称 //演示对函数名称ave的重载 #include<iostream> #include<stdlib.h> double ave(double n1,double n2); //返回两个数字n1和n2的平均值 double ave(double n1,double n2,double n3); //返回三个数字n1,n2,n3的平均值 int main() { using namespace std; cout<<"The average of 2.0,2.5 and 3.0 is " <<ave(2.0,2.5,3.0)<<endl;//这的ave()函数带3个参数 cout<<"The average of 4.5 and 5.5 is " <<ave(4.5,5.5)<<endl;//这的ave()函数带2个参数 system("pause"); return 0; } double ave(double n1,double n2)//这的ave()函数带2个参数 { return((n1+n2)/2.0); } double ave(double n1,double n2,double n3)//这的ave()函数带3个参数 { return((n1+n2+n3)/3.0); }

//3.16重载函数名称 //判断圆形比萨和矩形比萨，哪一种更适合购买 #include<iostream> #include<stdlib.h> double unitprice(int diameter,double price); //返回圆形比萨每平方英寸的价格，形参diameter是以英寸为单位 //的比萨直径，形参price是比萨的价格 double unitprice(int length,int width,double price); //返回矩形比萨每平方英寸的价格 //比萨的长度和宽度分别是length英寸和width英寸 //形参price是比萨的价格 int main() { using namespace std; int diameter ,length,width; double price_round,unit_price_round,price_rectangular, unitprice_rectangular; cout<<"Wlecome to the Pizza Consumers Union./n"; cout<<"Enter the diameter in inches of a round pizza: "; cin>>diameter; cout<<"Enter the price of a round pizza: $"; cin>>price_round; cout<<"Enter length and width in inches of a rectangular pizza: "; cin>>length>>width; cout<<"Enter the price of a rectangular pizza: $"; cin>>price_rectangular; //重载unitprice函数的使用 unitprice_rectangular=unitprice(length,width,price_rectangular); unit_price_round=unitprice(diameter,price_round); cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); cout<<endl <<"Round pizza: Diameter= " <<diameter<<" inches/n" <<"Price= $"<<price_round <<" Per square inch= $"<<unit_price_round <<endl <<"Rectangular pizza: Length= "<<length<<" inches/n" <<"Rectangular pizza: Width= "<<width<<" inches/n" <<"Price= $"<<price_rectangular <<" Per square inch= $"<<unitprice_rectangular <<endl; if(unit_price_round<unitprice_rectangular) { cout<<"The round one is the better buy./n"; } else { cout<<"The rectangular one is the better buy./n"; } cout<<"Buon Appetito!/n"; system("pause"); return 0; } double unitprice(int diameter,double price) { const double PI=3.14159; double radius,area; radius=diameter/static_cast<double>(2); area=PI*radius*radius; return(price/area); } double unitprice(int length,int width,double price) { double area=length*width; return(price/area); }

——2010.1210

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