我需要完全理解以下代码:
#include <iostream>
using namespace std;
double area(double length, double width);
double time(double p_area, double h_area, double mow_rate);
int main() {
double d_plot_length, d_plot_width, d_home_side, d_mow_rate;
double plot_area, home_area, time_taken;
// I've used double for all of these to get the most precise values possible, something I'd only really consider doing on small programmes such as this
cout << "What is the length of the plot? In meters please." << endl;
cin >> d_plot_length;
cout << "What is the width of the plot? In meters please." << endl;
cin >> d_plot_width;
cout<< "What is the size of the side of the house? In meters please." << endl;
cin >> d_home_side;
cout << "What is the rate at which you are going to be mowing? In meters per minute please" << endl;
cin >> d_mow_rate;
// Just getting all the data I need from the user
plot_area = area(d_plot_length, d_plot_width);
home_area = area(d_home_side, d_home_side);
time_taken = time(plot_area, home_area, d_mow_rate);
cout << "It will take " << time_taken << " minutes to mow this lawn. Better get cracking" << endl;
return 0;
}
double area(double length, double width) {
double value;
value = length * width;
return value;
}
double time(double p_area, double h_area, double mow_rate) {
double value;
value = (p_area - h_area) / mow_rate;
return value;
}
我正在努力理解time()
函数的工作原理。
到目前为止,我理解:
time_taken
,从time()
函数中获取其值:time(plot_area, home_area, d_mow_rate)
。
time()
函数从底部的函数声明中获取其值。
double time(double p_area, double h_area, double mow_rate) {
double value;
value = (p_area - h_area) / mow_rate;
return value;
}
但是,这就是我被困住的地方。系统会要求用户输入d_plot_length
,d_plot_width
等的值。因此,我无法理解编译器如何知道这些值p_area
和h_area
实际上是什么。
我意识到area()
函数在某种程度上用于帮助time()
函数,但据我所知P_area
中的变量time()
等函数没有赋值给它们。
请有人填补我理解中的空白。
更准确地说,我想确切地知道time_taken
在屏幕上显示的过程,从过程的开始到cout
。就像我说我熟悉大多数领域但不是全部。
答案 0 :(得分:1)
在您的程序中,您计算了以下值:
plot_area = area(d_plot_length, d_plot_width); home_area = area(d_home_side, d_home_side);
调用方法area(double,double)
时,生成的double
值将存储在这些变量中。
然后你有函数调用:
time_taken = time(plot_area, home_area, d_mow_rate);
这是按值调用类型的函数调用。变量中的值副本plot_area
,home_area
和d_mow_rate
将传递给函数。在time(double, double, double)
中,计算是在您在此方法中定义的逻辑的基础上完成的,并且结果值将返回到main()
方法中的函数调用。
请注意,函数调用是call by value
,因此只有值的副本传递给函数time(double, double, double)
中提到的参数,即使main()
中的变量名称相同。 1}}和函数调用。
如需进一步阅读,我建议您查看以下链接: